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backends/drm: combine matrix operations in the right order

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Matrix multiplication is right to left, so the operations have to be added
in the reverse order from the list
This commit is contained in:
Xaver Hugl 2024-07-17 19:00:41 +02:00
parent cd1b70ef05
commit 75075fdb89
1 changed files with 6 additions and 2 deletions
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8
src/backends/drm/drm_colorop.cpp
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@ -11,6 +11,8 @@
#include "drm_commit.h"
#include "drm_object.h"
#include <ranges>
namespace KWin
{
@ -202,9 +204,10 @@ static uint64_t doubleToFixed(double value)
void LegacyMatrixColorOp::program(DrmAtomicCommit *commit, std::span<const ColorOp> operations, double inputScale, double outputScale)
{
// NOTE that matrix operations have to be added in reverse order to get the correct result!
QMatrix4x4 result;
result.scale(1.0 / inputScale);
for (const auto &op : operations) {
result.scale(outputScale);
for (const auto &op : operations | std::views::reverse) {
if (auto matrix = std::get_if<ColorMatrix>(&op.operation)) {
result *= matrix->mat;
} else if (auto mult = std::get_if<ColorMultiplier>(&op.operation)) {
@ -213,6 +216,7 @@ void LegacyMatrixColorOp::program(DrmAtomicCommit *commit, std::span<const Color
Q_UNREACHABLE();
}
}
result.scale(1.0 / inputScale);
drm_color_ctm data = {
.matrix = {
doubleToFixed(result(0, 0)), doubleToFixed(result(0, 1)), doubleToFixed(result(0, 2)), //