From 55e794203a26486d8067e669f7cb298026ba2a61 Mon Sep 17 00:00:00 2001
From: Andri Yngvason <andri@yngvason.is>
Date: Wed, 1 May 2024 13:24:35 +0000
Subject: [PATCH] render: Add region of interest to
 wlr_texture_read_pixels_options

This adds a region of interest option, outside of which data need not be
copied.
---
 include/wlr/render/wlr_texture.h |  2 ++
 render/gles2/texture.c           | 14 +++++++++++++-
 render/pixman/renderer.c         |  5 ++++-
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/include/wlr/render/wlr_texture.h b/include/wlr/render/wlr_texture.h
index 1e352c6e6..bc66e7d54 100644
--- a/include/wlr/render/wlr_texture.h
+++ b/include/wlr/render/wlr_texture.h
@@ -37,6 +37,8 @@ struct wlr_texture_read_pixels_options {
 	uint32_t dst_x, dst_y;
 	/** Source box of the texture to read from. If empty, the full texture is assumed. */
 	const struct wlr_box src_box;
+	/** Region of interest within source box. If NULL, the full region is assumed to be of interest. */
+	struct pixman_region32 *roi;
 };
 
 bool wlr_texture_read_pixels(struct wlr_texture *texture,
diff --git a/render/gles2/texture.c b/render/gles2/texture.c
index f9ad4cc56..c22f56b32 100644
--- a/render/gles2/texture.c
+++ b/render/gles2/texture.c
@@ -215,7 +215,19 @@ static bool gles2_texture_read_pixels(struct wlr_texture *wlr_texture,
 		// Under these particular conditions, we can read the pixels with only
 		// one glReadPixels call
 
-		glReadPixels(src.x, src.y, src.width, src.height, fmt->gl_format, fmt->gl_type, p);
+		int y_offset = 0;
+		int src_height = src.height;
+		int data_offset = 0;
+		if (options->roi) {
+			struct pixman_box32 *ext =
+				pixman_region32_extents(options->roi);
+			y_offset = ext->y1;
+			src_height = ext->y2 - ext->y1;
+			data_offset = y_offset * options->stride;
+		}
+
+		glReadPixels(src.x, src.y + y_offset, src.width, src_height,
+				fmt->gl_format, fmt->gl_type, p + data_offset);
 	} else {
 		// Unfortunately GLES2 doesn't support GL_PACK_ROW_LENGTH, so we have to read
 		// the lines out row by row
diff --git a/render/pixman/renderer.c b/render/pixman/renderer.c
index a5b83e38e..71cec0cd6 100644
--- a/render/pixman/renderer.c
+++ b/render/pixman/renderer.c
@@ -107,9 +107,12 @@ static bool texture_read_pixels(struct wlr_texture *wlr_texture,
 	pixman_image_t *dst = pixman_image_create_bits_no_clear(fmt,
 			src.width, src.height, p, options->stride);
 
+	if (options->roi) {
+		pixman_image_set_clip_region32(dst, options->roi);
+	}
+
 	pixman_image_composite32(PIXMAN_OP_SRC, texture->image, NULL, dst,
 			src.x, src.y, 0, 0, 0, 0, src.width, src.height);
-
 	pixman_image_unref(dst);
 
 	return true;