From 505f92e73339f57b775a1afacadf261c9caf134c Mon Sep 17 00:00:00 2001
From: Consolatis <35009135+Consolatis@users.noreply.github.com>
Date: Sun, 12 Jun 2022 21:11:25 +0200
Subject: [PATCH] src/buffer: Automatically adapt to scale attribute

Based on discussion in PR #389
---
 include/buffer.h |  2 ++
 src/buffer.c     | 15 ++++++++++++++-
 src/osd.c        |  4 +---
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/buffer.h b/include/buffer.h
index af833f00..59ec3f12 100644
--- a/include/buffer.h
+++ b/include/buffer.h
@@ -37,6 +37,8 @@ struct lab_data_buffer {
 	uint32_t format;
 	size_t stride;
 	bool free_on_destroy;
+	uint32_t unscaled_width;
+	uint32_t unscaled_height;
 };
 
 /* Create a buffer which creates a new cairo CAIRO_FORMAT_ARGB32 surface */
diff --git a/src/buffer.c b/src/buffer.c
index 44891005..1c64276a 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -92,10 +92,23 @@ buffer_create_cairo(uint32_t width, uint32_t height, float scale,
 	if (!buffer) {
 		return NULL;
 	}
-	wlr_buffer_init(&buffer->base, &data_buffer_impl, width, height);
+	buffer->unscaled_width = width;
+	buffer->unscaled_height = height;
+	width *= scale;
+	height *= scale;
 
+	/* Allocate the buffer with the scaled size */
+	wlr_buffer_init(&buffer->base, &data_buffer_impl, width, height);
 	cairo_surface_t *surf =
 		cairo_image_surface_create(CAIRO_FORMAT_ARGB32, width, height);
+
+	/**
+	 * Tell cairo about the device scale so we can keep drawing in unscaled
+	 * coordinate space. Pango will automatically use the cairo scale attribute
+	 * as well when creating text on this surface.
+	 *
+	 * For a more complete explanation see PR #389
+	 */
 	cairo_surface_set_device_scale(surf, scale, scale);
 
 	buffer->cairo = cairo_create(surf);
diff --git a/src/osd.c b/src/osd.c
index b057d01f..153f5379 100644
--- a/src/osd.c
+++ b/src/osd.c
@@ -129,13 +129,11 @@ osd_update(struct server *server)
 		float scale = output->wlr_output->scale;
 		int w = (OSD_ITEM_WIDTH + (2 * OSD_BORDER_WIDTH));
 		int h = get_osd_height(&server->views);
-		int scaled_w = w * scale;
-		int scaled_h = h * scale;
 
 		if (output->osd_buffer) {
 			wlr_buffer_drop(&output->osd_buffer->base);
 		}
-		output->osd_buffer = buffer_create_cairo(scaled_w, scaled_h, scale, true);
+		output->osd_buffer = buffer_create_cairo(w, h, scale, true);
 
 		cairo_t *cairo = output->osd_buffer->cairo;
 		cairo_surface_t *surf = cairo_get_target(cairo);