fixed delayed shader loads leading to incorrect rendering and crashes (dynamic lights)

changelog.txt

@@ -25,6 +25,8 @@ chg: with r_backend GL3, depth fade with MSAA now requires GLSL 4.00 at a minimu
 
 chg: with r_backend GL3, alpha to coverage now requires GLSL 4.00 at a minimum
 
+fix: delayed shader loads could lead to incorrect rendering and crashes (mostly with dynamic lights)
+
 fix: the nextdemo variable wasn't used to start the playback of a new demo when:
   - a drop error happened during demo playback
   - the engine failed to open the current demo file

code/renderer/tr_local.h

@@ -508,6 +508,7 @@ struct drawSurf_t {
 	qhandle_t				model;		// MD3 model handle
 	int						index;		// transparent surface's registration order
 	float					shaderSort;	// transparent surface's shader sort
+	int						shaderNum;	// unsorted shader index, for when we need to do fix-ups
 };
 
 extern void (*rb_surfaceTable[SF_NUM_SURFACE_TYPES])( const void* );
@@ -515,6 +516,7 @@ extern void (*rb_surfaceTable[SF_NUM_SURFACE_TYPES])( const void* );
 
 struct litSurf_t {
 	unsigned sort;						// bit combination for fast compares
+	int shaderNum;						// unsorted shader index, for when we need to do fix-ups
 	const surfaceType_t* surface;		// any of surface*_t
 	litSurf_t* next;
 };

code/renderer/tr_main.cpp

@@ -1074,6 +1074,7 @@ void R_AddDrawSurf( const surfaceType_t* surface, const shader_t* shader, int fo
 	drawSurf->sort = R_ComposeSort( tr.currentEntityNum, shader, fogIndex );
 	drawSurf->surface = surface;
 	drawSurf->model = tr.currentModel != NULL ? tr.currentModel->index : 0;
+	drawSurf->shaderNum = shader->index;
 }
 
 
@@ -1087,6 +1088,7 @@ void R_AddLitSurf( const surfaceType_t* surface, const shader_t* shader, int fog
 	litSurf_t* const litSurf = &tr.refdef.litSurfs[tr.refdef.numLitSurfs++];
 	litSurf->sort = R_ComposeSort( tr.currentEntityNum, shader, fogIndex );
 	litSurf->surface = surface;
+	litSurf->shaderNum = shader->index;
 
 	if (!tr.light->head)
 		tr.light->head = litSurf;

code/renderer/tr_shader.cpp

@@ -1552,6 +1552,33 @@ static void SortNewShader()
 	for ( i = 0; i < tr.numShaders; ++i ) {
 		tr.sortedShaders[i]->sortedIndex = i;
 	}
+
+	//
+	// If we register a new shader when surfaces are already added,
+	// the decoded sorted shader index for the added surfaces will not always be correct anymore.
+	// This can lead to incorrect rendering (wrong shader used)
+	// and potentially crashes too (lit surfaces referencing shaders with no diffuse stage).
+	// We'll therefore update all surfaces that have already been added for this entire frame,
+	// not just the last view. Hence why we don't use firstDrawSurf / firstLitSurf.
+	// The extra CPU cost for the fix-up is nothing compared to loading new textures mid-frame.
+	//
+
+	int entityNum, fogNum;
+	const shader_t* wrongShader;
+
+	const int numDrawSurfs = tr.refdef.numDrawSurfs;
+	drawSurf_t* drawSurfs = tr.refdef.drawSurfs;
+	for( int i = 0; i < numDrawSurfs; ++i, ++drawSurfs ) {
+		R_DecomposeSort( drawSurfs->sort, &entityNum, &wrongShader, &fogNum );
+		drawSurfs->sort = R_ComposeSort( entityNum, tr.shaders[drawSurfs->shaderNum], fogNum );
+	}
+
+	const int numLitSurfs = tr.refdef.numLitSurfs;
+	litSurf_t* litSurfs = tr.refdef.litSurfs;
+	for ( int i = 0; i < numLitSurfs; ++i, ++litSurfs ) {
+		R_DecomposeSort( litSurfs->sort, &entityNum, &wrongShader, &fogNum );
+		litSurfs->sort = R_ComposeSort( entityNum, tr.shaders[litSurfs->shaderNum], fogNum );
+	}
 }