vtk/0002-Use-GL_DRAW_BUFFER0-instead-of-GL_DRAW_BUFFER-for-GL.patch

From 068773541005f8d8f027b373a01c821788439c8b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20Br=C3=BCns?= <stefan.bruens@rwth-aachen.de>
Date: Sun, 21 Nov 2021 22:51:36 +0100
Subject: [PATCH] Use GL_DRAW_BUFFER0 instead of GL_DRAW_BUFFER for GLES
 compatibility

ARB_draw_buffers is part of GL 2.0, so GL_DRAW_BUFFERS0 is always
available, and contrary to GL_DRAW_BUFFER it is also valid for GLES
(part of GLES 3 or as EXT_draw_buffers).

This also matches the universal use of glDrawBuffers instead of
glDrawBuffer.

At least with MESA, GL_DRAW_BUFFER and GL_DRAW_BUFFER0 always return the
same value. GL_DRAW_BUFFERn is also used in several places already.
---
 .../ContextOpenGL2/vtkOpenGLContextBufferId.cxx      |  2 +-
 .../ContextOpenGL2/vtkOpenGLContextDevice2DPrivate.h |  2 +-
 Rendering/External/vtkExternalOpenGLRenderWindow.cxx |  2 +-
 Rendering/OpenGL2/vtkOpenGLRenderWindow.cxx          |  8 ++++----
 Rendering/OpenGL2/vtkOpenGLState.cxx                 | 12 ++++++------
 5 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/Rendering/ContextOpenGL2/vtkOpenGLContextBufferId.cxx b/Rendering/ContextOpenGL2/vtkOpenGLContextBufferId.cxx
index c0e0f8909f..dd6a93bde3 100644
--- a/Rendering/ContextOpenGL2/vtkOpenGLContextBufferId.cxx
+++ b/Rendering/ContextOpenGL2/vtkOpenGLContextBufferId.cxx
@@ -139,7 +139,7 @@ vtkIdType vtkOpenGLContextBufferId::GetPickedItem(int x, int y)
       // Render texture to current write buffer. Texel x,y is rendered at
       // pixel x,y (instead of pixel 0,0 to work around pixel ownership test).
       GLint savedDrawBuffer;
-      glGetIntegerv(GL_DRAW_BUFFER, &savedDrawBuffer);
+      glGetIntegerv(GL_DRAW_BUFFER0, &savedDrawBuffer);
 
       vtkOpenGLState::ScopedglEnableDisable dsaver(ostate, GL_DEPTH_TEST);
       vtkOpenGLState::ScopedglEnableDisable ssaver(ostate, GL_STENCIL_TEST);
diff --git a/Rendering/ContextOpenGL2/vtkOpenGLContextDevice2DPrivate.h b/Rendering/ContextOpenGL2/vtkOpenGLContextDevice2DPrivate.h
index 29e5f47671..7acb87e25f 100644
--- a/Rendering/ContextOpenGL2/vtkOpenGLContextDevice2DPrivate.h
+++ b/Rendering/ContextOpenGL2/vtkOpenGLContextDevice2DPrivate.h
@@ -309,7 +309,7 @@ public:
       this->SavedStencilTest = ostate->GetEnumState(GL_STENCIL_TEST);
       this->SavedBlend = ostate->GetEnumState(GL_BLEND);
       ostate->vtkglGetFloatv(GL_COLOR_CLEAR_VALUE, this->SavedClearColor);
-      ostate->vtkglGetIntegerv(GL_DRAW_BUFFER, &this->SavedDrawBuffer);
+      ostate->vtkglGetIntegerv(GL_DRAW_BUFFER0, &this->SavedDrawBuffer);
     }
   }
 
diff --git a/Rendering/External/vtkExternalOpenGLRenderWindow.cxx b/Rendering/External/vtkExternalOpenGLRenderWindow.cxx
index 445bfce802..5e1f2f4b24 100644
--- a/Rendering/External/vtkExternalOpenGLRenderWindow.cxx
+++ b/Rendering/External/vtkExternalOpenGLRenderWindow.cxx
@@ -58,7 +58,7 @@ void vtkExternalOpenGLRenderWindow::Start()
 
   // For stereo, render the correct eye based on the OpenGL buffer mode
   GLint bufferType;
-  ostate->vtkglGetIntegerv(GL_DRAW_BUFFER, &bufferType);
+  ostate->vtkglGetIntegerv(GL_DRAW_BUFFER0, &bufferType);
   vtkCollectionSimpleIterator sit;
   vtkRenderer* renderer;
   for (this->GetRenderers()->InitTraversal(sit);
diff --git a/Rendering/OpenGL2/vtkOpenGLRenderWindow.cxx b/Rendering/OpenGL2/vtkOpenGLRenderWindow.cxx
index 25b521bd0d..426aa69f08 100644
--- a/Rendering/OpenGL2/vtkOpenGLRenderWindow.cxx
+++ b/Rendering/OpenGL2/vtkOpenGLRenderWindow.cxx
@@ -583,8 +583,8 @@ bool vtkOpenGLRenderWindow::GetUsingSRGBColorSpace()
     this->MakeCurrent();
 
     GLint attachment = GL_BACK_LEFT;
-#ifdef GL_DRAW_BUFFER
-    glGetIntegerv(GL_DRAW_BUFFER, &attachment);
+#ifdef GL_DRAW_BUFFER0
+    glGetIntegerv(GL_DRAW_BUFFER0, &attachment);
 #endif
     // GL seems odd with its handling of left/right.
     // if it says we are using GL_FRONT or GL_BACK
@@ -639,8 +639,8 @@ int vtkOpenGLRenderWindow::GetColorBufferSizes(int* rgba)
   {
     this->MakeCurrent();
     GLint attachment = GL_BACK_LEFT;
-#ifdef GL_DRAW_BUFFER
-    glGetIntegerv(GL_DRAW_BUFFER, &attachment);
+#ifdef GL_DRAW_BUFFER0
+    glGetIntegerv(GL_DRAW_BUFFER0, &attachment);
 #endif
 #ifdef GL_ES_VERSION_3_0
     // GLES only has the GL_BACK color
diff --git a/Rendering/OpenGL2/vtkOpenGLState.cxx b/Rendering/OpenGL2/vtkOpenGLState.cxx
index 24f23a5c44..aca4e4f247 100644
--- a/Rendering/OpenGL2/vtkOpenGLState.cxx
+++ b/Rendering/OpenGL2/vtkOpenGLState.cxx
@@ -217,8 +217,8 @@ void vtkOpenGLState::CheckState()
     error = true;
   }
   unsigned int sval;
-#ifdef GL_DRAW_BUFFER
-  ::glGetIntegerv(GL_DRAW_BUFFER, iparams);
+#ifdef GL_DRAW_BUFFER0
+  ::glGetIntegerv(GL_DRAW_BUFFER0, iparams);
   sval = cs.DrawBinding.GetDrawBuffer(0);
   if (sval == GL_BACK_LEFT)
   {
@@ -504,8 +504,8 @@ void vtkOpenGLState::vtkglBindFramebuffer(unsigned int target, unsigned int val)
     {
       cs.DrawBinding.Binding = val;
       ::glBindFramebuffer(GL_DRAW_FRAMEBUFFER, val);
-#ifdef GL_DRAW_BUFFER
-      ::glGetIntegerv(GL_DRAW_BUFFER, (int*)&cs.DrawBinding.DrawBuffers[0]);
+#ifdef GL_DRAW_BUFFER0
+      ::glGetIntegerv(GL_DRAW_BUFFER0, (int*)&cs.DrawBinding.DrawBuffers[0]);
 #endif
     }
   }
@@ -1626,8 +1626,8 @@ void vtkOpenGLState::ResetFramebufferBindings()
 {
   auto& cs = this->Stack.top();
   ::glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, (int*)&cs.DrawBinding.Binding);
-#ifdef GL_DRAW_BUFFER
-  ::glGetIntegerv(GL_DRAW_BUFFER, (int*)&cs.DrawBinding.DrawBuffers[0]);
+#ifdef GL_DRAW_BUFFER0
+  ::glGetIntegerv(GL_DRAW_BUFFER0, (int*)&cs.DrawBinding.DrawBuffers[0]);
 #endif
 
   ::glGetIntegerv(GL_READ_FRAMEBUFFER_BINDING, (int*)&cs.ReadBinding.Binding);
-- 
2.33.1