try more to match Skia's alpha type for source and destination

This is an extension of the other recent commit, matching alpha type
is faster, and knowing the content is opaque should also allow
more optimizations.

Change-Id: I632d3f50e3f4729a64403c3c3ed1b79d63f0c5dd
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/104046
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

2 files changed, 17 insertions, 3 deletions

diff --git a/vcl/inc/skia/salbmp.hxx b/vcl/inc/skia/salbmp.hxx
index 0cd48c8c46c2..49aabcf69a7f 100644
--- a/vcl/inc/skia/salbmp.hxx
+++ b/vcl/inc/skia/salbmp.hxx
@@ -82,6 +82,8 @@ public:
     // Returns true if it is known that this bitmap can be ignored if it's to be used
     // as an alpha bitmap. An optimization, not guaranteed to return true for all such cases.
     bool IsFullyOpaqueAsAlpha() const;
+    // Alpha type best suitable for the content.
+    SkAlphaType alphaType() const;
 
 #ifdef DBG_UTIL
     void dump(const char* file) const;
diff --git a/vcl/inc/skia/utils.hxx b/vcl/inc/skia/utils.hxx
index b3a2045eea96..00feccedfdae 100644
--- a/vcl/inc/skia/utils.hxx
+++ b/vcl/inc/skia/utils.hxx
@@ -37,11 +37,23 @@ void disableRenderMethod(RenderMethod method);
 
 // Create SkSurface, GPU-backed if possible.
 VCL_DLLPUBLIC sk_sp<SkSurface> createSkSurface(int width, int height,
-                                               SkColorType type = kN32_SkColorType);
+                                               SkColorType type = kN32_SkColorType,
+                                               SkAlphaType alpha = kPremul_SkAlphaType);
 
-inline sk_sp<SkSurface> createSkSurface(const Size& size, SkColorType type = kN32_SkColorType)
+inline sk_sp<SkSurface> createSkSurface(const Size& size, SkColorType type = kN32_SkColorType,
+                                        SkAlphaType alpha = kPremul_SkAlphaType)
 {
-    return createSkSurface(size.Width(), size.Height(), type);
+    return createSkSurface(size.Width(), size.Height(), type, alpha);
+}
+
+inline sk_sp<SkSurface> createSkSurface(int width, int height, SkAlphaType alpha)
+{
+    return createSkSurface(width, height, kN32_SkColorType, alpha);
+}
+
+inline sk_sp<SkSurface> createSkSurface(const Size& size, SkAlphaType alpha)
+{
+    return createSkSurface(size.Width(), size.Height(), kN32_SkColorType, alpha);
 }
 
 // Create SkImage, GPU-backed if possible.