From b5fc3d2a7e4b3e8c9fbb50bae1d7840da0db9234 Mon Sep 17 00:00:00 2001
From: KIU Shueng Chuan <nixchuan@gmail.com>
Date: Sat, 17 Jul 2021 10:40:27 +0800
Subject: [PATCH] add comment about definition of viewport

---
 pyqtgraph/opengl/GLViewWidget.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/pyqtgraph/opengl/GLViewWidget.py b/pyqtgraph/opengl/GLViewWidget.py
index c9113d44..7bf09f4d 100644
--- a/pyqtgraph/opengl/GLViewWidget.py
+++ b/pyqtgraph/opengl/GLViewWidget.py
@@ -230,6 +230,8 @@ class GLViewWidget(QtWidgets.QOpenGLWidget):
         if viewport is None:
             glViewport(*self.getViewport())
         else:
+            # note: the following code means that we have defined "viewport"
+            #       to be in device pixels.
             glViewport(*viewport)
         self.setProjection(region=region)
         self.setModelview()