From b0b185112dd75e774abdd0252fd0dbe6d601b1ba Mon Sep 17 00:00:00 2001
From: Matthew Waters <matthew@centricular.com>
Date: Tue, 7 May 2024 23:04:04 +1000
Subject: [PATCH] glmemory: use the GL stride calculation also for downloading
 into sysmem

Allows writing into sysmem with arbitrary strides.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6795>
---
 .../gst-plugins-base/gst-libs/gst/gl/gstglmemory.c    | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/subprojects/gst-plugins-base/gst-libs/gst/gl/gstglmemory.c b/subprojects/gst-plugins-base/gst-libs/gst/gl/gstglmemory.c
index 7658ea1f32..331c1fec46 100644
--- a/subprojects/gst-plugins-base/gst-libs/gst/gl/gstglmemory.c
+++ b/subprojects/gst-plugins-base/gst-libs/gst/gl/gstglmemory.c
@@ -71,6 +71,10 @@ GST_DEBUG_CATEGORY_STATIC (GST_CAT_GL_MEMORY);
 #define GL_UNPACK_ROW_LENGTH 0x0CF2
 #endif
 
+#ifndef GL_PACK_ROW_LENGTH
+#define GL_PACK_ROW_LENGTH 0x0D02
+#endif
+
 #ifndef GL_TEXTURE_RECTANGLE
 #define GL_TEXTURE_RECTANGLE 0x84F5
 #endif
@@ -459,6 +463,13 @@ gst_gl_memory_read_pixels (GstGLMemory * gl_mem, gpointer write_pointer)
     }
   }
 
+  if (USING_OPENGL (context) || USING_GLES3 (context)
+      || USING_OPENGL3 (context)) {
+    gl->PixelStorei (GL_PACK_ROW_LENGTH, gl_mem->unpack_length);
+  } else if (USING_GLES2 (context)) {
+    gl->PixelStorei (GL_PACK_ALIGNMENT, gl_mem->unpack_length);
+  }
+
   _gst_gl_memory_start_log (gl_mem, "glReadPixels");
   gl->ReadPixels (0, 0, gl_mem->tex_width, GL_MEM_HEIGHT (gl_mem), format,
       type, write_pointer);