OpenGL: use GL_CLAMP_TO_EDGE with Linear filter

Engine/gfx/ali3dogl.cpp

@@ -36,8 +36,6 @@
 
 #if AGS_OPENGL_ES2
 
-#define GL_CLAMP GL_CLAMP_TO_EDGE
-
 const char* fbo_extension_string = "GL_OES_framebuffer_object";
 
 #define glGenFramebuffersEXT glGenFramebuffers
@@ -1130,18 +1128,20 @@ void OGLGraphicsDriver::_renderSprite(const OGLDrawListEntry *drawListEntry,
     {
       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
     }
     else if (_do_render_to_texture)
     {
       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
+      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
     }
     else
     {
       _filter->SetFilteringForStandardSprite();
     }
-    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
-    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
 
     if (txdata->_vertex != nullptr)
     {
@@ -1639,8 +1639,12 @@ void OGLGraphicsDriver::UpdateTextureRegion(OGLTextureTile *tile, Bitmap *bitmap
   else
     BitmapToVideoMem(bitmap, has_alpha, &fixedTile, memPtr, pitch, usingLinearFiltering);
 
-  // Mimic the behaviour of GL_CLAMP_EDGE for the tile edges
-  // NOTE: on some platforms GL_CLAMP_EDGE does not work with the version of OpenGL we're using.
+  // Mimic the behaviour of GL_CLAMP_TO_EDGE for the tile edges
+  // NOTE: on some platforms GL_CLAMP_TO_EDGE does not work with the version of OpenGL we're using.
+  // TODO: test the GL version to see if this is even necessary?!
+  // Info on CLAMP types:
+  // https://docs.gl/gl2/glTexParameter
+  // https://stackoverflow.com/questions/56823126/how-is-gl-clamp-in-opengl-different-from-gl-clamp-to-edge
   if (tile->width < tileWidth)
   {
     if (tilex > 0)

Engine/gfx/gfxfilter_aaogl.cpp

@@ -37,6 +37,10 @@ void AAOGLGfxFilter::SetFilteringForStandardSprite()
 {
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+    // Prevent sprite pixels mixing with "texture border" pixels sometimes
+    // See: https://stackoverflow.com/questions/56823126/how-is-gl-clamp-in-opengl-different-from-gl-clamp-to-edge
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 }
 
 const GfxFilterInfo &AAOGLGfxFilter::GetInfo() const

Engine/gfx/gfxfilter_ogl.cpp

@@ -37,6 +37,8 @@ void OGLGfxFilter::SetFilteringForStandardSprite()
 {
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
 }
 
 const GfxFilterInfo &OGLGfxFilter::GetInfo() const

Engine/gfx/ogl_headers.h

@@ -38,3 +38,9 @@
 #ifndef GLAPI
 #define GLAD_GL_VERSION_2_0 (0)
 #endif
+
+#if AGS_OPENGL_ES2
+#ifndef GL_CLAMP
+    #define GL_CLAMP GL_CLAMP_TO_EDGE
+#endif
+#endif // AGS_OPENGL_ES2