commit fb9fed53893f6a5e46fde5c3822994c67e09fb71
author Roman Stratiienko <r.stratiienko@gmail.com> Thu Jan 23 02:25:12 2025 +0200
committer Roman Stratiienko <r.stratiienko@gmail.com> Wed Feb 05 22:39:35 2025 +0200
tree c6902ea64c19529504e9ef16002f66c8caef825e
parent 4e15bfc9481019f98e34aa5458537ca467b7e11b

drm_hwcomposer: Use float type to store alpha internally

0.0-1.0F range is a natural way to store alpha value internally,
to be converted later to DRM-specific 0-0xFFFF fixed point type at
DRM layer.

Change-Id: Iedf2b11e53bf38efd08cd4eda1346647b9ff721f
Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>

compositor/LayerData.h

diff --git a/compositor/LayerData.h b/compositor/LayerData.h
index 127b3ff..962141f 100644
--- a/compositor/LayerData.h
+++ b/compositor/LayerData.h
@@ -60,9 +60,11 @@
   std::optional<IRect> i_rect;
 };
 
+constexpr float kAlphaOpaque = 1.0F;
+
 struct PresentInfo {
   LayerTransform transform{};
-  uint16_t alpha = UINT16_MAX;
+  float alpha = kAlphaOpaque;
   SrcRectInfo source_crop{};
   DstRectInfo display_frame{};
 

drm/DrmPlane.cpp

diff --git a/drm/DrmPlane.cpp b/drm/DrmPlane.cpp
index 76846d5..36f29b7 100644
--- a/drm/DrmPlane.cpp
+++ b/drm/DrmPlane.cpp
@@ -289,7 +289,9 @@
     return -EINVAL;
   }
 
-  if (alpha_property_ && !alpha_property_.AtomicSet(pset, layer.pi.alpha)) {
+  if (alpha_property_ &&
+      !alpha_property_.AtomicSet(pset,
+                                 std::lround(layer.pi.alpha * UINT16_MAX))) {
     return -EINVAL;
   }
 

hwc2_device/HwcLayer.cpp

diff --git a/hwc2_device/HwcLayer.cpp b/hwc2_device/HwcLayer.cpp
index 1d1e118..6940c12 100644
--- a/hwc2_device/HwcLayer.cpp
+++ b/hwc2_device/HwcLayer.cpp
@@ -46,8 +46,7 @@
     layer_data_.pi.display_frame = layer_properties.display_frame.value();
   }
   if (layer_properties.alpha) {
-    layer_data_.pi.alpha = std::lround(layer_properties.alpha.value() *
-                                       UINT16_MAX);
+    layer_data_.pi.alpha = layer_properties.alpha.value();
   }
   if (layer_properties.source_crop) {
     layer_data_.pi.source_crop = layer_properties.source_crop.value();