Bug corrections concerning the cursor in editor

gfx.asm

@@ -8,6 +8,7 @@
   .export         _gfx_init
   .export         _gfx_fill
   .export         _gfx_pixel
+  .export         _gfx_get_pixel
   .export         _gfx_refresh
 
 
@@ -101,7 +102,6 @@ init_end:
 ;**************************
 ;void __fastcall__ gfx_fill( uint8_t color )
 ; Fills the screen with the given color
-; TMP1 and PTR1 and PTR2 are overwritten
 _gfx_fill:
 ; TODO SWITCH PAGES !!
         ;saving the context
@@ -258,6 +258,65 @@ oddeven:
         RTS
 
 
+;**************************
+;uint8_t __fastcall__ gfx_get_pixel( uint8_t coord_x, uint8_t coord_y )
+; Returns the pixel's color
+_gfx_get_pixel:
+        TAX         ; coord_y
+
+        ;saving the context
+        LDA ptr1
+        JSR pusha
+        LDA ptr2
+        JSR pusha
+
+        ; Page's address to ptr1
+        LDA #<Page1
+        STA ptr1
+        LDA #>Page1
+        STA ptr1+1
+        ; Line's adress to ptr2
+        TXA
+        LSR
+        ASL
+        TAY
+        LDA (ptr1),Y
+        STA ptr2
+        INY
+        LDA (ptr1),Y
+        STA ptr2+1
+        ; get coord_x
+        LDY #2      ;there were 4 pushes to save registers
+        LDA (sp),Y
+        TAY
+        TXA
+        AND #1  ; test line parity to read the correct nybble
+        BEQ even_2
+odd_2:    LDA (ptr2),Y
+          LSR  ; color is in lo nybble
+          LSR
+          LSR
+          LSR
+          CLC
+          BCC end_2
+even_2:   LDA (ptr2),Y
+          AND #$0F  ; color is in hi nybble
+end_2:  TAX
+
+        ;restoring the context
+        JSR popa
+        STA ptr2
+        JSR popa
+        STA ptr1
+        JSR popa  ;1st parameter
+
+        ; return value
+        TXA
+        LDX #0
+
+        RTS
+
+
 ;**************************
 ;void __fastcall__ gfx_refresh( void )
 ; Updates the screen by displaying the Future Page which becomes Current

gfx.h

@@ -1,11 +1,18 @@
 #ifndef __GFX_H__
 #define __GFX_H__
 
-
+// Restores text mode
 void __fastcall__ mode_text( void );
+// Switches to the desired res and mode.
+// Always displays page 1
 void __fastcall__ gfx_init( uint8_t resolution, uint8_t mode );
+// Fills the screen with the given color
 void __fastcall__ gfx_fill( uint8_t color );
+// Draws a pixel at the given coordinates
 void __fastcall__ gfx_pixel( uint8_t color, uint8_t coord_x, uint8_t coord_y );
+// Returns the pixel's color
+uint8_t __fastcall__ gfx_get_pixel( uint8_t coord_x, uint8_t coord_y );
+// Updates the screen by displaying the Future Page which becomes Current
 void __fastcall__ gfx_refresh( void );
 
 enum eMode {

gol_apple2.c

@@ -147,12 +147,6 @@ void draw_cells( void ) {
     }
 }
 
-void clear_cursor( const uint8_t x, const uint8_t y )
-{
-  if( Cells[x][y] == DEAD ) {
-    gfx_pixel( BLACK, x, y );
-  }
-}
 
 void editor( void )
 {
@@ -162,9 +156,11 @@ void editor( void )
     #define KEY_RIGHT   'l'
 
     uint8_t quit, x, y;
+    uint8_t color_pixel;
 
     x = NB_COLUMNS >> 1u;
-    y = NB_LINES >> 1u;
+    y = (NB_LINES >> 1u) + 1;
+    color_pixel = gfx_get_pixel( x, y );
 
     quit = 0;
     while ( quit == 0)
@@ -172,19 +168,19 @@ void editor( void )
         KeyPressed = cgetc();
         switch (KeyPressed) {
         case KEY_LEFT:
-                clear_cursor(x,y);
+                gfx_pixel( color_pixel, x, y );
                 if( x > 1u ) { --x; }
           break;
         case KEY_DOWN:
-                clear_cursor(x,y);
+                gfx_pixel( color_pixel, x, y );
                 if( y < NB_LINES-2u ) { ++y; }
           break;
         case KEY_UP:
-                clear_cursor(x,y);
+                gfx_pixel( color_pixel, x, y );
                 if( y > 1u ) { --y; }
           break;
         case KEY_RIGHT:
-                clear_cursor(x,y);
+                gfx_pixel( color_pixel, x, y );
                 if( x < NB_COLUMNS-2u ) {	++x; }
           break;
         case ' ':
@@ -198,6 +194,7 @@ void editor( void )
           quit = 1;
           break;
         }
+        color_pixel = gfx_get_pixel( x, y );
         gfx_pixel( WHITE, x, y ); //cursor
     }
 
@@ -228,16 +225,16 @@ void run( void  )
     uint16_t nb_iterations = 2u;
     KeyPressed = NO_KEY;
 
-    cursor(0);
-    gotoxy( 0u, NB_LINES );
-    printf("Iteration:1     (R)eset (E)ditor (Q)uit");
+    //cursor(0);
+    //gotoxy( 0u, NB_LINES );
+    //printf("Iteration:1     (R)eset (E)ditor (Q)uit");
     while( KeyPressed == NO_KEY)
     {
         /* Evolving the cells */
         update( );
         /* Printing iterations */
-        gotoxy(10u, NB_LINES);
-        printf( itoa(nb_iterations++, str_nb_iteration, 10) );
+        //gotoxy(10u, NB_LINES);
+        //printf( itoa(nb_iterations++, str_nb_iteration, 10) );
         /* Testing key pressed */
         if( kbhit() ) {
             KeyPressed = cgetc();