GL: Make updateTexture invalidate texture on change of texture unit

Switching texture units means the value of lastTextureUsed could be
invalid, meaning we need to unconditionally re-bind and update parameters.

A future optimization would be to keep a per-texture-unit cache, so
that we wouldn't have to re-bind and set parameters when switching
units back and forth, but this complicates the current code somewhat,
so it's left for another patch.

Change-Id: Icb2a5d03457a907f3c25bbb437feeb7c5f155716
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@theqtcompany.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/gui/opengl/qopenglpaintengine_p.h b/src/gui/opengl/qopenglpaintengine_p.h
index 209cd3d7b5..297ac54640 100644
--- a/src/gui/opengl/qopenglpaintengine_p.h
+++ b/src/gui/opengl/qopenglpaintengine_p.h
@@ -69,6 +69,8 @@ enum EngineMode {
 QT_BEGIN_NAMESPACE
 
 #define GL_STENCIL_HIGH_BIT         GLuint(0x80)
+#define QT_UNKNOWN_TEXTURE_UNIT     GLuint(-1)
+#define QT_DEFAULT_TEXTURE_UNIT     GLuint(0)
 #define QT_BRUSH_TEXTURE_UNIT       GLuint(0)
 #define QT_IMAGE_TEXTURE_UNIT       GLuint(0) //Can be the same as brush texture unit
 #define QT_MASK_TEXTURE_UNIT        GLuint(1)
@@ -184,6 +186,7 @@ public:
             snapToPixelGrid(false),
             nativePaintingActive(false),
             inverseScale(1),
+            lastTextureUnitUsed(QT_UNKNOWN_TEXTURE_UNIT),
             lastMaskTextureUsed(0)
     { }
 
@@ -199,6 +202,7 @@ public:
     void updateTexture(GLenum textureUnit, const T &texture, GLenum wrapMode, GLenum filterMode, TextureUpdateMode updateMode = UpdateIfNeeded);
     template<typename T>
     GLuint bindTexture(const T &texture);
+    void activateTextureUnit(GLenum textureUnit);
 
     void resetGLState();
 
@@ -300,6 +304,7 @@ public:
     GLfloat pmvMatrix[3][3];
     GLfloat inverseScale;
 
+    GLenum lastTextureUnitUsed;
     GLuint lastTextureUsed;
     GLuint lastMaskTextureUsed;