OpenGL: add gpuMatrixUpdate_legacy function

Marks matrix state as dirty so shader will use the latest values from glScale, glTranslate, etc.

We'll remove this after transitioning 100% to the new matrix API, which handles this sort of thing automatically.

Part of T49450

source/blender/gpu/GPU_matrix.h

@@ -133,6 +133,9 @@ const float *gpuGetNormalMatrixInverse(float m[3][3]);
 #if SUPPORT_LEGACY_MATRIX
 /* copy top matrix from each legacy stack into new fresh stack */
 void gpuMatrixBegin3D_legacy(void);
+
+/* call after using glScale, glTranslate, etc. between draw calls */
+void gpuMatrixUpdate_legacy(void);
 #endif
 
 

source/blender/gpu/intern/gpu_matrix.c

@@ -699,3 +699,11 @@ bool gpuMatricesDirty()
 {
 	return state.dirty;
 }
+
+#if SUPPORT_LEGACY_MATRIX
+void gpuMatrixUpdate_legacy()
+{
+	BLI_assert(state.mode == MATRIX_MODE_INACTIVE);
+	state.dirty = true;
+}
+#endif