From 3026218eaa0d3be59a898939da5126ca03bc5969 Mon Sep 17 00:00:00 2001
From: Nathan Reiner <nathan@nathanreiner.xyz>
Date: Mon, 10 Apr 2023 21:54:37 +0200
Subject: add double buffering

---
 config.h |  2 +-
 drw.c    | 26 ++++++++++++++++++++------
 drw.h    |  2 ++
 swt.c    |  1 +
 4 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/config.h b/config.h
index d279ed3..321f89b 100644
--- a/config.h
+++ b/config.h
@@ -21,7 +21,7 @@ static FontPath fonts[] = {
 		"/usr/share/fonts/gnu-free/FreeMonoBoldOblique.otf"                       /* Bold-Italic */
 	},
 };
-static int fontsize = 32;
+static int fontsize = 12;
 static int borderpx = 2;
 
 /*
diff --git a/drw.c b/drw.c
index dc220dc..79f4ab1 100644
--- a/drw.c
+++ b/drw.c
@@ -53,7 +53,7 @@ create_drw(struct wl_shm *shm, unsigned width, unsigned height)
 		return NULL;
 	}
 
-	canvas->data = mmap(
+	canvas->buffer_data = mmap(
 			NULL,
 			canvas->size,
 			PROT_READ | PROT_WRITE,
@@ -62,10 +62,8 @@ create_drw(struct wl_shm *shm, unsigned width, unsigned height)
 			0
 		);
 
-	if (canvas->data == MAP_FAILED) {
-		close(fd);
-		return NULL;
-	}
+	if (canvas->buffer_data == MAP_FAILED)
+		die("mmap failed: ");
 
 	pool = wl_shm_create_pool(
 			shm,
@@ -85,6 +83,14 @@ create_drw(struct wl_shm *shm, unsigned width, unsigned height)
 	wl_shm_pool_destroy(pool);
 	close(fd);
 
+	fd = allocate_shm_file(canvas->size);
+	canvas->data = mmap(NULL, canvas->size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
+
+	if (canvas->data == MAP_FAILED)
+		die("mmap failed: ");
+
+	close(fd);
+
 	return canvas;
 }
 
@@ -93,10 +99,18 @@ void
 free_drw(Canvas *canvas)
 {
 	munmap(canvas->data, canvas->size);
+	munmap(canvas->buffer_data, canvas->size);
 	free(canvas);
 }
 
 
+void
+push_buffer(Canvas *canvas)
+{
+	memcpy(canvas->buffer_data, canvas->data, canvas->size);
+}
+
+
 void
 draw_point(Canvas *canvas, unsigned x, unsigned y, uint32_t color)
 {
@@ -159,7 +173,7 @@ font_cache_generate_box(FontCache *fontcache)
 	Font *font = get_font_with_charcode(fontcache, 0);
 	FT_Set_Pixel_Sizes(font->face, 0, fontcache->fontsize);
 	fprintf(stderr, "fontsize: %i\n", fontcache->fontsize);
-	fontcache->box.width = (font->face->bbox.xMax - font->face->bbox.xMin) >> 6;
+	fontcache->box.width = (font->face->size->metrics.max_advance) >> 6;
 	fontcache->box.height = (font->face->size->metrics.height) >> 6;
 	fprintf(stderr, "width: %i, height: %i\n", fontcache->box.width, fontcache->box.height);
 }
diff --git a/drw.h b/drw.h
index 578fd2a..821e80e 100644
--- a/drw.h
+++ b/drw.h
@@ -11,6 +11,7 @@
 /* type definitions */
 typedef struct {
 	uint32_t *data;
+	uint32_t *buffer_data;
 	unsigned width;
 	unsigned height;
 	unsigned size;
@@ -61,6 +62,7 @@ typedef struct {
 /* exported functions */
 Canvas* create_drw(struct wl_shm *shm, unsigned width, unsigned height);
 void free_drw(Canvas *canvas);
+void push_buffer(Canvas *canvas);
 
 void draw_rect(Canvas *canvas, unsigned x, unsigned y, unsigned width, unsigned height, uint32_t color);
 void draw_point(Canvas *canvas, unsigned x, unsigned y, uint32_t color);
diff --git a/swt.c b/swt.c
index 860a85e..9c05200 100644
--- a/swt.c
+++ b/swt.c
@@ -288,6 +288,7 @@ draw_frame()
 void
 commit_surface()
 {
+	push_buffer(win.canvas);
 	wl_surface_attach(win.surface.wl, win.canvas->buffer, 0, 0);
 	wl_surface_damage_buffer(win.surface.wl, 0, 0, win.width, win.height);
 	wl_surface_commit(win.surface.wl);
-- 
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