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402 lines
12 KiB
ArmAsm
402 lines
12 KiB
ArmAsm
;
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; Graphics driver for the 320 pixels across, 200 pixels down, 256 colors mode
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; on the Commander X16
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;
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; 2020-07-02, Greg King <gregdk@users.sf.net>
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;
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.include "zeropage.inc"
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.include "tgi-kernel.inc"
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.include "tgi-error.inc"
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.include "cbm_kernal.inc"
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.include "cx16.inc"
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.macpack generic
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.macpack module
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; Macro that copies a word into a pseudo-register
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.mac setReg reg, src
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lda src
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ldx src+1
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sta gREG::reg
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stx gREG::reg+1
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.endmac
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; ------------------------------------------------------------------------
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; Header. Includes jump table and constants.
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module_header _cx320p1_tgi ; 320 pixels across, 1 pixel per byte
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; First part of the header is a structure that has a signature,
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; and defines the capabilities of the driver.
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.byte $74, $67, $69 ; ASCII "tgi"
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.byte TGI_API_VERSION ; TGI API version number
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.addr $0000 ; Library reference
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.word 320 ; X resolution
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.word 200 ; Y resolution
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.byte <$0100 ; Number of drawing colors
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.byte 1 ; Number of screens available
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.byte 8 ; System font X size
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.byte 8 ; System font Y size
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.word $0100 ; Aspect ratio (based on VGA display)
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.byte 0 ; TGI driver flags
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; Next, comes the jump table. Currently, all entries must be valid,
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; and may point to an RTS for test versions (function not implemented).
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.addr INSTALL
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.addr UNINSTALL
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.addr INIT
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.addr DONE
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.addr GETERROR
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.addr CONTROL
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.addr CLEAR
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.addr SETVIEWPAGE
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.addr SETDRAWPAGE
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.addr SETCOLOR
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.addr SETPALETTE
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.addr GETPALETTE
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.addr GETDEFPALETTE
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.addr SETPIXEL
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.addr GETPIXEL
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.addr LINE
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.addr BAR
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.addr TEXTSTYLE
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.addr OUTTEXT
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; ------------------------------------------------------------------------
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; Constant
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GRAPH320 = $80
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; ------------------------------------------------------------------------
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; Data
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; Variables mapped to the zero-page segment variables. Some of these are
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; used for passing parameters to the driver.
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X1 := ptr1
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Y1 := ptr2
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X2 := ptr3
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Y2 := ptr4
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; Absolute variables used in the code
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.bss
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; The colors are indicies into a TGI palette. The TGI palette is indicies into
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; VERA's palette. Vera's palette is a table of Red, Green, and Blue levels.
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; The first 16 RGB elements mimic the Commodore 64's colors.
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defpalette: .res $0100
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palette: .res $0100
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bcolor := palette + 0 ; Background color
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color: .res 1 ; Stroke and fill index
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mode: .res 1 ; Old text mode
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.data
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error: .byte TGI_ERR_OK ; Error code
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.code
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; ------------------------------------------------------------------------
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; INSTALL routine. Is called after the driver is loaded into memory. May
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; initialize anything that has to be done just once. Is probably empty
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; most of the time.
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;
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; Must set an error code: NO
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INSTALL:
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; Create the default palette.
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ldx #$00
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: txa
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sta defpalette,x
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inx
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bnz :-
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; Fall through.
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; ------------------------------------------------------------------------
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; UNINSTALL routine. Is called before the driver is removed from memory. May
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; clean up anything done by INSTALL, but is probably empty most of the time.
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;
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; Must set an error code: NO
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UNINSTALL:
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rts
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; ------------------------------------------------------------------------
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; INIT: Changes an already installed device from text mode to graphics
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; mode.
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; Note that INIT/DONE may be called multiple times while the driver
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; is loaded, while INSTALL is called only once; so, any code that is needed
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; to initiate variables and so on must go here. Setting the palette is not
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; needed because that is called by the graphics kernel later.
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; The graphics kernel never will call INIT when a graphics mode already is
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; active, so there is no need to protect against that.
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;
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; Must set an error code: YES
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INIT: stz error ; #TGI_ERR_OK
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; Save the current text mode.
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lda SCREEN_MODE
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sta mode
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; Switch into (320 x 200 x 256) graphics mode.
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lda #GRAPH320
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jmp SCREEN_SET_MODE
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; ------------------------------------------------------------------------
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; DONE: Will be called to switch the graphics device back into text mode.
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; The graphics kernel never will call DONE when no graphics mode is active,
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; so there is no need to protect against that.
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;
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; Must set an error code: NO
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DONE:
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; Work around a prerelease 37 Kernal bug.
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; VERA (graphics) layer 0 isn't disabled by SCREEN_SET_MODE.
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stz VERA::CTRL
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lda VERA::DISP::VIDEO
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and #<~VERA::DISP::ENABLE::LAYER0
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sta VERA::DISP::VIDEO
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lda mode
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jmp SCREEN_SET_MODE
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; ------------------------------------------------------------------------
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; GETERROR: Return the error code in .A, and clear it.
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GETERROR:
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lda error
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stz error
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rts
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; ------------------------------------------------------------------------
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; CONTROL: Platform-/driver-specific entry point.
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;
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; Must set an error code: YES
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CONTROL:
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lda #TGI_ERR_INV_FUNC
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sta error
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rts
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; ------------------------------------------------------------------------
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; CLEAR: Clear the screen.
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;
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; Must set an error code: NO
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CLEAR := GRAPH_CLEAR
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; ------------------------------------------------------------------------
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; SETVIEWPAGE: Set the visible page. Called with the new page in .A (0..n-1).
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; The page number already is checked to be valid by the graphics kernel.
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;
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; Must set an error code: NO (will be called only if page OK)
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SETVIEWPAGE:
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; Fall through.
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; ------------------------------------------------------------------------
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; SETDRAWPAGE: Set the drawable page. Called with the new page in .A (0..n-1).
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; The page number already is checked to be valid by the graphics kernel.
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;
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; Must set an error code: NO (will be called only if page OK)
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SETDRAWPAGE:
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rts
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; ------------------------------------------------------------------------
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; SETPALETTE: Set the palette (not available with all drivers/hardware).
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; A pointer to the palette is passed in ptr1. Must set an error if palettes
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; are not supported
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;
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; Must set an error code: YES
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SETPALETTE:
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stz error ; #TGI_ERR_OK
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ldy #$00
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: lda (ptr1),y
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sta palette,y
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iny
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bnz :-
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lda color ; Get stroke and fill index
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; Fall through.
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; ------------------------------------------------------------------------
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; SETCOLOR: Set the drawing color (in .A). The new color already is checked
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; to be in a valid range (0..maxcolor).
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;
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; Must set an error code: NO (will be called only if color OK)
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SETCOLOR:
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tax
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sta color
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lda palette,x ; Set stroke and fill color
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tax
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ldy bcolor ; Get background color
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jmp GRAPH_SET_COLORS
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; ------------------------------------------------------------------------
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; GETPALETTE: Return the current palette in .XA. Even drivers that cannot
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; set the palette should return the default palette here, so there's no
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; way for this function to fail.
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;
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; Must set an error code: NO
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GETPALETTE:
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lda #<palette
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ldx #>palette
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rts
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; ------------------------------------------------------------------------
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; GETDEFPALETTE: Return the default palette for the driver in .XA. All
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; drivers should return something reasonable here, even drivers that don't
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; support palettes, otherwise the caller has no way to determine the colors
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; of the (not changable) palette.
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;
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; Must set an error code: NO (all drivers must have a default palette)
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GETDEFPALETTE:
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lda #<defpalette
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ldx #>defpalette
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rts
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; ------------------------------------------------------------------------
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; SETPIXEL: Draw one pixel at X1/Y1 = ptr1/ptr2 with the current drawing
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; color. The co-ordinates passed to this function never are outside the
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; visible screen area, so there is no need for clipping inside this function.
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;
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; Must set an error code: NO
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SETPIXEL:
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jsr Point
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jsr FB_CURSOR_POSITION
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ldx color
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lda palette,x
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jmp FB_SET_PIXEL
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; ------------------------------------------------------------------------
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; GETPIXEL: Read the color value of a pixel, and return it in .XA. The
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; co-ordinates passed to this function never are outside the visible screen
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; area, so there is no need for clipping inside this function.
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GETPIXEL:
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jsr Point
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jsr FB_CURSOR_POSITION
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jsr FB_GET_PIXEL
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ldx #>$0000
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rts
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; ------------------------------------------------------------------------
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; LINE: Draw a line from X1/Y1 to X2/Y2, where X1/Y1 = ptr1/ptr2 and
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; X2/Y2 = ptr3/ptr4, using the current drawing color.
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;
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; Must set an error code: NO
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LINE: jsr Point
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setReg r2, X2
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setReg r3, Y2
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jmp GRAPH_DRAW_LINE
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; ------------------------------------------------------------------------
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; BAR: Draw a filled rectangle with the corners X1/Y1, X2/Y2, where
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; X1/Y1 = ptr1/ptr2 and X2/Y2 = ptr3/ptr4, using the current drawing color.
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; Contrary to most other functions, the graphics kernel will sort and clip
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; the co-ordinates before calling the driver; so on entry, the following
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; conditions are valid:
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; X1 <= X2
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; Y1 <= Y2
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; (X1 >= 0) && (X1 < XRES)
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; (X2 >= 0) && (X2 < XRES)
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; (Y1 >= 0) && (Y1 < YRES)
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; (Y2 >= 0) && (Y2 < YRES)
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;
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; Must set an error code: NO
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BAR:
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; Set the starting corner.
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jsr Point
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; Set the width.
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lda X2
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sub X1
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sta gREG::r2
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lda X2+1
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sbc X1+1
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sta gREG::r2+1
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; Set the height.
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lda Y2
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sub Y1
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sta gREG::r3
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lda Y2+1
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sbc Y1+1
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sta gREG::r3+1
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; Set the corner radius.
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stz gREG::r4
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stz gREG::r4+1
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sec ; Fill the rectangle
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jmp GRAPH_DRAW_RECT
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; ------------------------------------------------------------------------
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; TEXTSTYLE: Set the style used when calling OUTTEXT. Text scaling in X and Y
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; directions are passed in .X and .Y, the text direction is passed in .A.
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;
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; Must set an error code: NO
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TEXTSTYLE:
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rts
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; ------------------------------------------------------------------------
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; OUTTEXT: Output text at X/Y = ptr1/ptr2 using the current color and the
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; current text style. The text to output is given as a zero-terminated
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; string with address in ptr3.
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;
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; Must set an error code: NO
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OUTTEXT:
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jsr Point
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ldy #$00
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@next: lda (ptr3),y
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bze @end
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phy
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jsr GRAPH_PUT_CHAR
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ply
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iny
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bnz @next
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@end: rts
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; ------------------------------------------------------------------------
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; Point: Set the arguments for the first point of a Kernal graphics function.
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Point: setReg r0, X1
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setReg r1, Y1
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rts
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