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GRAPHICS: Add comments about safe divisions in VectorRendererSpec.cpp.

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This commit is contained in:
Johannes Schickel 2016-02-21 14:41:29 +01:00
parent 7b9c15634f
commit 16aac72b60
1 changed files with 6 additions and 2 deletions
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8
graphics/VectorRendererSpec.cpp
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@ -441,13 +441,14 @@ template<typename PixelType>
void VectorRendererSpec<PixelType>:: void VectorRendererSpec<PixelType>::
gradientFill(PixelType *ptr, int width, int x, int y) { gradientFill(PixelType *ptr, int width, int x, int y) {
bool ox = ((y & 1) == 1); bool ox = ((y & 1) == 1);
int stripSize;
int curGrad = 0; int curGrad = 0;
while (_gradIndexes[curGrad + 1] <= y) while (_gradIndexes[curGrad + 1] <= y)
curGrad++; curGrad++;
stripSize = _gradIndexes[curGrad + 1] - _gradIndexes[curGrad]; // precalcGradient assures that _gradIndexes entries always differ in
// their value. This assures stripSize is always different from zero.
int stripSize = _gradIndexes[curGrad + 1] - _gradIndexes[curGrad];
int grad = (((y - _gradIndexes[curGrad]) % stripSize) << 2) / stripSize; int grad = (((y - _gradIndexes[curGrad]) % stripSize) << 2) / stripSize;
@ -1422,6 +1423,9 @@ drawTriangleVertAlg(int x1, int y1, int w, int h, bool inverted, PixelType color
blendPixelPtr(floor, color, 50); blendPixelPtr(floor, color, 50);
#if FIXED_POINT #if FIXED_POINT
// In this branch dx is always different from zero. This is because
// abs(dx) is strictly greater than abs(dy), and abs returns zero
// as minimal value.
int gradient = (dy << 8) / dx; int gradient = (dy << 8) / dx;
int intery = (y1 << 8) + gradient; int intery = (y1 << 8) + gradient;
#else #else