112 lines
3.0 KiB
NASM
112 lines
3.0 KiB
NASM
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; generic text drawing routines
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; draw a single font tile to a framebuffer
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; inputs:
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; r0: tile number
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; r1: X coordinate
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; r2: Y coordinate
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; r3: foreground color
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; r4: background color
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; r5: pointer to font graphics
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; r6: font width
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; r7: font height
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; r8: pointer to framebuffer
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; r9: framebuffer width (pixels)
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; outputs:
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; none
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draw_font_tile_generic:
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push r0
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push r1
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push r2
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push r5
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push r6
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push r7
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push r8
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push r9
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;movz.8 r0, r0 ; ensure the tile number is a single byte
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; calculate pointer to the tile data
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push r6
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mul r6, r7
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mul r0, r6
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mul r0, 4 ; 4 bytes per pixel
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add r0, r5 ; r0: pointer to tile data
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pop r6
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; calculate pointer to the framebuffer
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mul r9, 4 ; 4 bytes per pixel
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mul r2, r9 ; y * width * 4
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mul r1, 4 ; x * 4
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add r1, r2 ; y * width * 4 + (x * 4)
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add r1, r8 ; r1: pointer to framebuffer
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; r8: font width in bytes
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mov r8, r6
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mul r8, 4
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draw_font_tile_generic_y_loop:
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mov r5, r6 ; x counter
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draw_font_tile_generic_x_loop:
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mov r2, [r0]
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cmp r2, 0xFF000000
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ifz jmp draw_font_tile_generic_x_loop_background
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; drawing foreground pixel
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cmp r3, 0x00000000 ; is the foreground color supposed to be transparent?
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ifz jmp draw_font_tile_generic_x_loop_end
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mov [r1], r3 ; draw foreground color
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jmp draw_font_tile_generic_x_loop_end
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draw_font_tile_generic_x_loop_background:
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; drawing background pixel
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cmp r4, 0x00000000 ; is the background color supposed to be transparent?
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ifz jmp draw_font_tile_generic_x_loop_end
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mov [r1], r4 ; draw background color
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draw_font_tile_generic_x_loop_end:
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add r0, 4 ; increment tile pointer
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add r1, 4 ; increment framebuffer pointer
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dec r5
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ifnz jmp draw_font_tile_generic_x_loop ; loop if there are still more X pixels to draw
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sub r1, r8 ; return to the beginning of this line
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add r1, r9 ; increment to the next line by adding the framebuffer width in bytes
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dec r7 ; decrement height counter
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ifnz jmp draw_font_tile_generic_y_loop ; loop if there are still more Y pixels to draw
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pop r9
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pop r8
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pop r7
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pop r6
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pop r5
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pop r2
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pop r1
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pop r0
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ret
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; draw text to a framebuffer
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; inputs:
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; r0: pointer to null-terminated string
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; r1: X coordinate
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; r2: Y coordinate
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; r3: foreground color
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; r4: background color
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; r5: pointer to font graphics
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; r6: font width
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; r7: font height
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; r8: pointer to framebuffer
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; r9: framebuffer width
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; outputs:
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; r1: X coordinate of end of text
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draw_str_generic:
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push r0
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push r10
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mov r10, r0
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draw_str_generic_loop:
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movz.8 r0, [r10]
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call draw_font_tile_generic
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inc r10
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add r1, r6
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cmp.8 [r10], 0x00
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ifnz jmp draw_str_generic_loop
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pop r10
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pop r0
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ret
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