Slight refactor of VBO code to deal with multiple textures.

Added compareDrawSettings callback to driver mesh's callbacks which are
drawing textured faces (mapped and not mapped). This new callback checks
if two faces are drawing with the same settings (testures, shading etc)
and if they not, flush of faces happens into ogl using glDrawArrays and
next face would be drawn with it's own settings.

Currently implemented compareDrawSettings is used to resolve issue from
bug report only, probably there are extra places where this callback is
needed, but haven't seen configuration where current logic will fail,
so it should be ok.

Also reordered arguments passing to drawMappedFaces DM's callbacks,
so now all drawing callback are accepting list of callbacks and then
userData, instead of using mixed order of callbacks and userData which
was a bit confusing to work with.

This commit fixes:
- #26410: VBO & multitexture doesnt work
- #29464: VBO enabled causes UV coruption

1 files changed, 58 insertions, 42 deletions

diff --git a/source/blender/blenkernel/intern/cdderivedmesh.c b/source/blender/blenkernel/intern/cdderivedmesh.c
index 0f9033ca461..1c2537464c2 100644
--- a/source/blender/blenkernel/intern/cdderivedmesh.c
+++ b/source/blender/blenkernel/intern/cdderivedmesh.c
@@ -647,6 +647,7 @@ static void cdDM_drawFacesColored(DerivedMesh *dm, int useTwoSided, unsigned cha
 static void cdDM_drawFacesTex_common(DerivedMesh *dm,
 			   int (*drawParams)(MTFace *tface, int has_mcol, int matnr),
 			   int (*drawParamsMapped)(void *userData, int index),
+			   int (*compareDrawOptions)(void *userData, int cur_index, int next_index),
 			   void *userData) 
 {
 	CDDerivedMesh *cddm = (CDDerivedMesh*) dm;
@@ -771,24 +772,18 @@ static void cdDM_drawFacesTex_common(DerivedMesh *dm,
 		}
 
 		if( !GPU_buffer_legacy(dm) ) {
-			/* warning!, this logic is incorrect, see bug [#27175]
-			 * firstly, there are no checks for changes in context, such as texface image.
-			 * secondly, drawParams() sets the GL context, so checking if there is a change
-			 * from lastFlag is too late once glDrawArrays() runs, since drawing the arrays
-			 * will use the modified, OpenGL settings.
-			 * 
-			 * However its tricky to fix this without duplicating the internal logic
-			 * of drawParams(), perhaps we need an argument like...
-			 * drawParams(..., keep_gl_state_but_return_when_changed) ?.
-			 *
-			 * We could also just disable VBO's here, since texface may be deprecated - campbell.
-			 */
-			
+			int tottri = dm->drawObject->tot_triangle_point/3;
+			int next_actualFace= dm->drawObject->triangle_to_mface[0];
+
 			glShadeModel( GL_SMOOTH );
 			lastFlag = 0;
-			for(i = 0; i < dm->drawObject->tot_triangle_point/3; i++) {
-				int actualFace = dm->drawObject->triangle_to_mface[i];
+			for(i = 0; i < tottri; i++) {
+				int actualFace = next_actualFace;
 				int flag = 1;
+				int flush = 0;
+
+				if(i != tottri-1)
+					next_actualFace= dm->drawObject->triangle_to_mface[i+1];
 
 				if(drawParams) {
 					flag = drawParams(tf? &tf[actualFace]: NULL, (mcol != NULL), mf[actualFace].mat_nr);
@@ -804,27 +799,36 @@ static void cdDM_drawFacesTex_common(DerivedMesh *dm,
 						if(drawParamsMapped)
 							flag = drawParamsMapped(userData, actualFace);
 				}
-				if( flag != lastFlag ) {
-					if( startFace < i ) {
-						if( lastFlag != 0 ) { /* if the flag is 0 it means the face is hidden or invisible */
-							if (lastFlag==1 && col)
-								GPU_color_switch(1);
-							else
-								GPU_color_switch(0);
-							glDrawArrays(GL_TRIANGLES,startFace*3,(i-startFace)*3);
-						}
+
+				/* flush buffer if current triangle isn't drawable or it's last triangle */
+				flush= !flag || i == tottri - 1;
+
+				if(!flush && compareDrawOptions) {
+					int next_orig= (index==NULL) ? next_actualFace : index[next_actualFace];
+
+					if(orig==ORIGINDEX_NONE || next_orig==ORIGINDEX_NONE) {
+						flush= 1;
+					} else {
+						/* also compare draw options and flush buffer if they're different
+						   need for face selection highlight in edit mode */
+						flush|= compareDrawOptions(userData, orig, next_orig) == 0;
 					}
-					lastFlag = flag;
-					startFace = i;
 				}
-			}
-			if( startFace < dm->drawObject->tot_triangle_point/3 ) {
-				if( lastFlag != 0 ) { /* if the flag is 0 it means the face is hidden or invisible */
-					if (lastFlag==1 && col)
-						GPU_color_switch(1);
-					else
-						GPU_color_switch(0);
-					glDrawArrays(GL_TRIANGLES, startFace*3, dm->drawObject->tot_triangle_point - startFace*3);
+
+				if(flush) {
+					int first= startFace*3;
+					int count= (i-startFace+(flag ? 1 : 0))*3; /* Add one to the length if we're drawing at the end of the array */
+
+					if(count) {
+						if (col)
+							GPU_color_switch(1);
+						else
+							GPU_color_switch(0);
+
+						glDrawArrays(GL_TRIANGLES, first, count);
+					}
+
+					startFace = i + 1;
 				}
 			}
 		}
@@ -834,13 +838,19 @@ static void cdDM_drawFacesTex_common(DerivedMesh *dm,
 	}
 }
 
-static void cdDM_drawFacesTex(DerivedMesh *dm, int (*setDrawOptions)(MTFace *tface, int has_mcol, int matnr))
+static void cdDM_drawFacesTex(DerivedMesh *dm,
+			   int (*setDrawOptions)(MTFace *tface, int has_mcol, int matnr),
+			   int (*compareDrawOptions)(void *userData, int cur_index, int next_index),
+			   void *userData)
 {
-	cdDM_drawFacesTex_common(dm, setDrawOptions, NULL, NULL);
+	cdDM_drawFacesTex_common(dm, setDrawOptions, NULL, compareDrawOptions, userData);
 }
 
-static void cdDM_drawMappedFaces(DerivedMesh *dm, int (*setDrawOptions)(void *userData, int index, int *drawSmooth_r), void *userData, int useColors, int (*setMaterial)(int, void *attribs),
-			int (*compareDrawOptions)(void *userData, int cur_index, int next_index))
+static void cdDM_drawMappedFaces(DerivedMesh *dm,
+			int (*setDrawOptions)(void *userData, int index, int *drawSmooth_r),
+			int (*setMaterial)(int, void *attribs),
+			int (*compareDrawOptions)(void *userData, int cur_index, int next_index),
+			void *userData, int useColors)
 {
 	CDDerivedMesh *cddm = (CDDerivedMesh*) dm;
 	MVert *mv = cddm->mvert;
@@ -1009,9 +1019,12 @@ static void cdDM_drawMappedFaces(DerivedMesh *dm, int (*setDrawOptions)(void *us
 	}
 }
 
-static void cdDM_drawMappedFacesTex(DerivedMesh *dm, int (*setDrawOptions)(void *userData, int index), void *userData)
+static void cdDM_drawMappedFacesTex(DerivedMesh *dm,
+			   int (*setDrawOptions)(void *userData, int index),
+			   int (*compareDrawOptions)(void *userData, int cur_index, int next_index),
+			   void *userData)
 {
-	cdDM_drawFacesTex_common(dm, NULL, setDrawOptions, userData);
+	cdDM_drawFacesTex_common(dm, NULL, setDrawOptions, compareDrawOptions, userData);
 }
 
 static void cddm_draw_attrib_vertex(DMVertexAttribs *attribs, MVert *mvert, int a, int index, int vert, int smoothnormal)
@@ -1058,7 +1071,10 @@ static void cddm_draw_attrib_vertex(DMVertexAttribs *attribs, MVert *mvert, int
 	glVertex3fv(mvert[index].co);
 }
 
-static void cdDM_drawMappedFacesGLSL(DerivedMesh *dm, int (*setMaterial)(int, void *attribs), int (*setDrawOptions)(void *userData, int index), void *userData)
+static void cdDM_drawMappedFacesGLSL(DerivedMesh *dm,
+			   int (*setMaterial)(int, void *attribs),
+			   int (*setDrawOptions)(void *userData, int index),
+			   void *userData)
 {
 	CDDerivedMesh *cddm = (CDDerivedMesh*) dm;
 	GPUVertexAttribs gattribs;
@@ -1348,7 +1364,7 @@ static void cdDM_drawMappedFacesGLSL(DerivedMesh *dm, int (*setMaterial)(int, vo
 	glShadeModel(GL_FLAT);
 }
 
-static void cdDM_drawFacesGLSL(DerivedMesh *dm, int (*setMaterial)(int, void *attribs))
+static void cdDM_drawFacesGLSL(DerivedMesh *dm,int (*setMaterial)(int, void *attribs))
 {
 	dm->drawMappedFacesGLSL(dm, setMaterial, NULL, NULL);
 }