rhi: gl, metal, d3d: Reuse shader objects when source is the same

Now that Qt Quick's batch renderer misses one level of shader source
caching due to the nature of pipeline state objects, it can be useful
to keep and reuse shader objects when the hash of the source code
matches.

The goal here is to allow Qt Quick to be on par with what the direct
OpenGL path has when it comes to caching shader sources and compilation
results. The program binary disk cache is not in scope in this patch.

Also adds QRhi::releaseCachedResources(), similarly to what the scenegraph
has. This can be called to clear caches such as the shader object
cache we keep here.

Change-Id: Ie3d81d823f61fa65ec814439e882c498f7774d43
Reviewed-by: Christian Strømme <christian.stromme@qt.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/gui/rhi/qrhi_p.h b/src/gui/rhi/qrhi_p.h
index 2d36c19e99..928d1f8fa7 100644
--- a/src/gui/rhi/qrhi_p.h
+++ b/src/gui/rhi/qrhi_p.h
@@ -1420,6 +1420,8 @@ public:
     static const int MAX_LAYERS = 6; // cubemaps only
     static const int MAX_LEVELS = 16; // a width and/or height of 65536 should be enough for everyone
 
+    void releaseCachedResources();
+
 protected:
     QRhi();