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Fix clipping issue

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This commit is contained in:
jpirnay
2026-02-21 11:03:32 +01:00
parent e87106d4d4
commit 707782b6b5
1 changed files with 24 additions and 8 deletions
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lib/GfxRenderer/GfxRenderer.cpp
+24 -8
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@@ -178,17 +178,33 @@ static inline uint8_t bitmapExtract(const uint8_t* bitmap, const int bitPos, con
// Write up to 8 foreground bits into a physical framebuffer row.
// bits — MSB-aligned; bit 7 = pixel at phyBitPos, lower (8-count) bits are zero.
// phyBitPos — physical X of the MSB pixel; must be in [0, DISPLAY_WIDTH).
// phyBitPos — physical X of the MSB pixel; may be negative for left-edge partial chunks.
// pixelState true → black (clear bits to 0), false → white (set bits to 1).
static inline void writeRowBits(uint8_t* const row, const int phyBitPos, const uint8_t bits, const bool pixelState) {
const int byteIdx = phyBitPos >> 3;
const int shift = phyBitPos & 7;
if (pixelState) {
row[byteIdx] &= ~(bits >> shift);
if (shift > 0 && byteIdx + 1 < HalDisplay::DISPLAY_WIDTH_BYTES) row[byteIdx + 1] &= ~(uint8_t)(bits << (8 - shift));
uint8_t effectiveBits = bits;
int byteIdx;
int shift;
if (phyBitPos < 0) {
// Chunk starts off-screen left: clip by shifting out the off-screen MSBs.
// bits is MSB-aligned, so (bits << neg) discards the neg off-screen pixels
// and leaves the on-screen pixels MSB-aligned starting at physical X=0.
const int neg = -phyBitPos;
if (neg >= 8) return; // entire chunk is off-screen left
effectiveBits = bits << neg;
byteIdx = 0;
shift = 0;
} else {
row[byteIdx] |= (bits >> shift);
if (shift > 0 && byteIdx + 1 < HalDisplay::DISPLAY_WIDTH_BYTES) row[byteIdx + 1] |= (uint8_t)(bits << (8 - shift));
byteIdx = phyBitPos >> 3;
shift = phyBitPos & 7;
}
if (pixelState) {
row[byteIdx] &= ~(effectiveBits >> shift);
if (shift > 0 && byteIdx + 1 < HalDisplay::DISPLAY_WIDTH_BYTES)
row[byteIdx + 1] &= ~(uint8_t)(effectiveBits << (8 - shift));
} else {
row[byteIdx] |= (effectiveBits >> shift);
if (shift > 0 && byteIdx + 1 < HalDisplay::DISPLAY_WIDTH_BYTES)
row[byteIdx + 1] |= (uint8_t)(effectiveBits << (8 - shift));
}
}