; An overlay is a callback from the render to shadow in a range of lines. At a minimum, the overlay ; code needs to LDA/STA or TSB slam the data, but an overlay is typically used to draw some graphic ; on top of the rendered playfield, such as a status bar or in-game message ; ; This overlay implementation is for a status bar that is 8-lines height that will be used to display some ; status information. The interesting bit of this implementation is that it's split into two pieces, ; a left and right section in order to be able to use the same code for different screen widths, but ; still keep the content in the cornders while covering the full screen. ; ; There are two subroutines that need to be implemented -- one to update the overlay content and a ; second to actually render to the screen ; Initialize the overlay be drawin gin static content that will not change over time CHAR_TILE_BASE equ 193 ; set this to the real tile id that starts an ASCII run starting at '0' through 'Z' ; Define the sizes of the left and right overlay buffers R_CHAR_COUNT equ 8 ; "TICK:XXX" L_CHAR_COUNT equ 7 ; "FPS:XXX" ; Allocate a single buffer for holding both the left and right overlay characters + masks CHAR_WIDTH equ 4 OVRLY_SPAN equ {{L_CHAR_COUNT+R_CHAR_COUNT}*CHAR_WIDTH} ovrly_buff ds OVRLY_SPAN*8 ovrly_mask ds OVRLY_SPAN*8 r_line equ ovrly_buff+{L_CHAR_COUNT*CHAR_WIDTH} l_line equ ovrly_buff r_mask equ ovrly_mask+{L_CHAR_COUNT*CHAR_WIDTH} l_mask equ ovrly_mask MASK_OFFSET equ {ovrly_mask-ovrly_buff} InitOverlay lda #'F' ldy #l_line+{CHAR_WIDTH*0} jsr _DrawChar lda #'P' ldy #l_line+{CHAR_WIDTH*1} jsr _DrawChar lda #'S' ldy #l_line+{CHAR_WIDTH*2} jsr _DrawChar lda #':' ldy #l_line+{CHAR_WIDTH*3} jsr _DrawChar lda #'T' ldy #r_line+{CHAR_WIDTH*0} jsr _DrawChar lda #'I' ldy #r_line+{CHAR_WIDTH*1} jsr _DrawChar lda #'C' ldy #r_line+{CHAR_WIDTH*2} jsr _DrawChar lda #'K' ldy #r_line+{CHAR_WIDTH*3} jsr _DrawChar lda #':' ldy #r_line+{CHAR_WIDTH*4} jsr _DrawChar rts ; Update the dynamic content of the overlay _num2ascii and #$000F cmp #$000A bcc :out clc adc #'A'-'0'-10 :out clc adc #'0' rts UdtOverlay lda frameCount ; render the FPS value xba jsr _num2ascii ldy #l_line+{CHAR_WIDTH*4} jsr _DrawChar lda frameCount lsr lsr lsr lsr jsr _num2ascii ldy #l_line+{CHAR_WIDTH*5} jsr _DrawChar lda frameCount jsr _num2ascii ldy #l_line+{CHAR_WIDTH*6} jsr _DrawChar ldal OneSecondCounter ; reder the number of remaining seconds xba jsr _num2ascii ldy #r_line+{CHAR_WIDTH*5} jsr _DrawChar ldal OneSecondCounter lsr lsr lsr lsr jsr _num2ascii ldy #r_line+{CHAR_WIDTH*6} jsr _DrawChar ldal OneSecondCounter jsr _num2ascii ldy #r_line+{CHAR_WIDTH*7} jsr _DrawChar rts ; Draw the overlay ; A = address of the left edge of the screen Overlay ENT phb ; Called via JSL phk plb phd ; save the direct page register sta l_addr ; save this value (will go into D-reg later) clc adc #L_CHAR_COUNT*CHAR_WIDTH ; advance past the left characters sta m_addr ; this is the DP for the TSB slam lda l_addr clc adc ScreenWidth sec sbc #{R_CHAR_COUNT*CHAR_WIDTH} sta r_addr ; this is the DP for the right side ; Calculate the TSB slam entry point sec sbc m_addr ; calculate the number of words between the two ends and #$FFFE pha lda #m_end sec sbc 1,s sta m_patch+1 pla sei _R1W1 ldy #8 ; count the line we're on ldx #0 ovrly_loop lda r_addr tcd ; set the direct page for the right side jmp r_ovrly ; render that line r_ovrly_rtn lda m_addr tcd ; set the direct page for the slam in the middle lda #0 ; set to zero for TSB slam m_patch jmp $0000 ; jump into the slam field m_ovrly_rtn lda l_addr ; set the direct page for the left side tcd jmp l_ovrly l_ovrly_rtn clc tdc adc #160 ; advance to the next screen line sta l_addr adc #{L_CHAR_COUNT*CHAR_WIDTH} sta m_addr lda r_addr adc #160 sta r_addr txa adc #OVRLY_SPAN tax dey bne ovrly_loop _R0W0 cli :exit pld ; restore the direct page and bank and return plb rtl l_addr ds 2 m_addr ds 2 r_addr ds 2 r_ovrly ]idx equ 0 lup R_CHAR_COUNT lda ]idx and r_line+MASK_OFFSET+]idx,x ora r_line+]idx,x sta ]idx lda ]idx+2 and r_line+MASK_OFFSET+]idx+2,x ora r_line+]idx+2,x sta ]idx+2 ]idx equ ]idx+4 --^ jmp r_ovrly_rtn ; In R1W1, so can't use the stack l_ovrly ]idx equ 0 lup L_CHAR_COUNT lda ]idx and l_line+MASK_OFFSET+]idx,x ora l_line+]idx,x sta ]idx lda ]idx+2 and l_line+MASK_OFFSET+]idx+2,x ora l_line+]idx+2,x sta ]idx+2 ]idx equ ]idx+4 --^ jmp l_ovrly_rtn ; Single TSB slam m_line ]idx equ $9E lup 80 ; 80 words max for a full-width screen tsb ]idx ]idx equ ]idx-2 --^ m_end jmp m_ovrly_rtn ; Draw a character (tile) into a location of the overlay ; ; A = Tile ID ; Y = overlay address location tiledata EXT _DCOut rts _DrawChar cmp #'0' bcc _DCOut cmp #'Z'+1 bcs _DCOut sec sbc #'0' clc adc #CHAR_TILE_BASE jsl GetTileAddr tax ]idx equ 0 lup 8 ldal tiledata+32+{]idx*4},x sta: {]idx*OVRLY_SPAN}+MASK_OFFSET,y ldal tiledata+{]idx*4},x sta: {]idx*OVRLY_SPAN},y ldal tiledata+32+{]idx*4}+2,x sta: {]idx*OVRLY_SPAN}+MASK_OFFSET+2,y ldal tiledata+{]idx*4}+2,x sta: {]idx*OVRLY_SPAN}+2,y ]idx equ ]idx+1 --^ rts