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Optimization for ZX to LCD pixel rendering #34
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -145,33 +145,52 @@ void Renderer::drawSpectrumScreen() { | |
| } | ||
| uint16_t tftInkColor = specpal565[inkColor]; | ||
| uint16_t tftPaperColor = specpal565[paperColor]; | ||
| const uint32_t u32Lookup[4] = { | ||
| tftPaperColor | (tftPaperColor << 16), // 00 | ||
| tftPaperColor | (tftInkColor << 16), // 01 | ||
| tftInkColor | (tftPaperColor << 16), // 10 | ||
| tftInkColor | (tftInkColor << 16) // 11 | ||
| }; | ||
| for (int y = 0; y < 8; y++) | ||
| { | ||
| // read the value of the pixels | ||
| int screenY = attrY * 8 + y; | ||
| int col = ((attrX * 8) & B11111000) >> 3; | ||
| int scan = (screenY & B11000000) + ((screenY & B111) << 3) + ((screenY & B111000) >> 3); | ||
| uint8_t row = *(pixelBase + 32 * scan + col); | ||
| uint8_t rowCopy = *(pixelBaseCopy + 32 * scan + col); | ||
| int screenY = attrY * 8; | ||
| int scan = (screenY & B11000000) + (y << 3) + ((screenY & B111000) >> 3); | ||
| uint8_t row = *(pixelBase + 32 * scan + attrX); | ||
| uint8_t rowCopy = *(pixelBaseCopy + 32 * scan + attrX); | ||
| // check for changes in the pixel data | ||
| if (row != rowCopy) | ||
| { | ||
| dirty = true; | ||
| *(pixelBaseCopy + 32 * scan + col) = row; | ||
| *(pixelBaseCopy + 32 * scan + attrX) = row; | ||
| } | ||
| uint16_t *pixelAddress = pixelBuffer + 256 * y + attrX * 8; | ||
| for (int x = 0; x < 8; x++) | ||
| { | ||
| if (row & 128) | ||
| { | ||
| *pixelAddress = tftInkColor; | ||
| } | ||
| else | ||
| { | ||
| *pixelAddress = tftPaperColor; | ||
| } | ||
| pixelAddress++; | ||
| row = row << 1; | ||
| // Since the ESP32 is a 32-bit processor with a 32-bit memory bus, | ||
| // it's more efficient to write 32-bits at a time. So...calculate | ||
| // pairs of pixels and avoid conditional tests and branches. | ||
| // Check for the 2 optimal cases of pure foreground or background | ||
| if (row == 0) { | ||
| uint32_t u32Clr = tftPaperColor | (tftPaperColor << 16); | ||
| uint32_t *d32 = (uint32_t *)pixelAddress; | ||
| *d32++ = u32Clr; | ||
| *d32++ = u32Clr; | ||
| *d32++ = u32Clr; | ||
| *d32++ = u32Clr; | ||
| pixelAddress += 8; | ||
|
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. The Copilot uses AI. Check for mistakes. Positive FeedbackNegative Feedback |
||
| } else if (row == 0xff) { | ||
| uint32_t u32Clr = tftInkColor | (tftInkColor << 16); | ||
| uint32_t *d32 = (uint32_t *)pixelAddress; | ||
| *d32++ = u32Clr; | ||
| *d32++ = u32Clr; | ||
| *d32++ = u32Clr; | ||
| *d32++ = u32Clr; | ||
| pixelAddress += 8; | ||
|
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. The Copilot uses AI. Check for mistakes. Positive FeedbackNegative Feedback |
||
| } else { // Otherwise use a lookup table to write pairs of pixels | ||
| uint32_t *d32 = (uint32_t *)pixelAddress; | ||
| *d32++ = u32Lookup[row >> 6]; | ||
| *d32++ = u32Lookup[(row >> 4) & 3]; | ||
| *d32++ = u32Lookup[(row >> 2) & 3]; | ||
| *d32++ = u32Lookup[row & 3]; | ||
| } | ||
| } | ||
| } | ||
|
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The calculation of
screenYinside the loop is inefficient since it's constant for all iterations. Consider moving this calculation outside the loop as it was in the original code (screenY = attrY * 8 + y).Copilot uses AI. Check for mistakes.