Support png buttons

In the theme directory add close-{active,inactive}.png instead of
close.xbm - and similarly for iconify, menu and max.

docs/labwc-theme.5.scd

@@ -18,7 +18,8 @@ searched for in the following order:
 Choosing a theme is done by editing the <name> key in the <theme> section of
 the rc.xml configuration file (labwc-config(5)).
 
-A theme consists of a themerc file and optionally some xbm icons.
+A theme consists of a themerc file and optionally some titlebar icons (referred
+to as buttons).
 
 Theme settings specified in themerc can be overridden by creating a
 'themerc-override' file in the configuration directory, which is normally
@@ -175,19 +176,26 @@ elements are not listed here, but are supported.
 
 # BUTTONS
 
-The images used for the titlebar buttons are 1-bit xbm (X Bitmaps). These are
-masks where 0=clear and 1=colored. The xbm image files are placed in the same
-directory within your theme as the themerc file. Here are all the possible xbm
-files looked for:
+The images used for the titlebar icons are referred to as buttons.
+
+The image formats listed below are supported. They are listed in order of
+precedence, where the first format in the list is searched for first.
+
+- png
+- xbm
+
+By default, buttons are 1-bit xbm (X Bitmaps). These are masks where 0=clear and
+1=colored. The xbm image files are placed in the same directory as the themerc
+file within a particular theme. The following xbm buttons are supported:
 
 - max.xbm
 - iconify.xbm
 - close.xbm
 - menu.xbm
 
-More will be supported later.
-
-Note: menu.xbm is not part of openbox-3.6 spec
+One advantage of xbm buttons over other formats is that they change color based
+on the theme. Other formats use the suffices "-active" and "-inactive" to align
+with the respective titlebar colors. For example: "close-active.png"
 
 # DEFINITIONS
 

include/button-png.h

@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef LABWC_BUTTON_PNG_H
+#define LABWC_BUTTON_PNG_H
+
+struct lab_data_buffer;
+
+void png_load(const char *filename, struct lab_data_buffer **buffer);
+
+#endif /* LABWC_BUTTON_PNG_H */

meson.build

@@ -69,6 +69,7 @@ cairo = dependency('cairo')
 pangocairo = dependency('pangocairo')
 input = dependency('libinput', version: '>=1.14')
 math = cc.find_library('m')
+png = dependency('libpng')
 
 if get_option('xwayland').enabled() and not wlroots_has_xwayland
 	error('no wlroots Xwayland support')
@@ -103,6 +104,7 @@ labwc_deps = [
   pangocairo,
   input,
   math,
+  png,
 ]
 
 subdir('include')

src/button-png.c

@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) Johan Malm 2023
+ */
+#define _POSIX_C_SOURCE 200809L
+#include <cairo.h>
+#include <png.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <wlr/util/log.h>
+#include "buffer.h"
+#include "button-png.h"
+#include "common/dir.h"
+#include "labwc.h"
+#include "theme.h"
+
+/* Share with session.c:isfile() */
+static bool
+file_exists(const char *path)
+{
+	struct stat st;
+	return (!stat(path, &st));
+}
+
+/* Share with xbm.c:xbm_path() */
+static char *
+button_path(const char *filename)
+{
+	static char buffer[4096] = { 0 };
+	snprintf(buffer, sizeof(buffer), "%s/%s", theme_dir(rc.theme_name), filename);
+	return buffer;
+}
+
+/*
+ * cairo_image_surface_create_from_png() does not gracefully handle non-png
+ * files, so we verify the header before trying to read the rest of the file.
+ */
+#define PNG_BYTES_TO_CHECK (4)
+static bool
+ispng(const char *filename)
+{
+	unsigned char header[PNG_BYTES_TO_CHECK];
+	FILE *fp = fopen(filename, "rb");
+	if (!fp) {
+		return false;
+	}
+	if (fread(header, 1, PNG_BYTES_TO_CHECK, fp) != PNG_BYTES_TO_CHECK) {
+		fclose(fp);
+		return false;
+	}
+	if (png_sig_cmp(header, (png_size_t)0, PNG_BYTES_TO_CHECK)) {
+		wlr_log(WLR_ERROR, "file '%s' is not a recognised png file", filename);
+		fclose(fp);
+		return false;
+	}
+	fclose(fp);
+	return true;
+}
+
+#undef PNG_BYTES_TO_CHECK
+
+void
+png_load(const char *filename, struct lab_data_buffer **buffer)
+{
+	if (*buffer) {
+		wlr_buffer_drop(&(*buffer)->base);
+		*buffer = NULL;
+	}
+
+	char *path = button_path(filename);
+	if (!file_exists(path) || !ispng(path)) {
+		return;
+	}
+
+	cairo_surface_t *image = cairo_image_surface_create_from_png(path);
+	if (cairo_surface_status(image)) {
+		wlr_log(WLR_ERROR, "error reading png button '%s'", path);
+		cairo_surface_destroy(image);
+		return;
+	}
+	cairo_surface_flush(image);
+
+	double w = cairo_image_surface_get_width(image);
+	double h = cairo_image_surface_get_height(image);
+	*buffer = buffer_create_cairo((int)w, (int)h, 1.0, true);
+	cairo_t *cairo = (*buffer)->cairo;
+	cairo_set_source_surface(cairo, image, 0, 0);
+	cairo_paint_with_alpha(cairo, 1.0);
+}

src/meson.build

@@ -15,6 +15,7 @@ labwc_sources = files(
   'node.c',
   'osd.c',
   'output.c',
+  'button-png.c',
   'regions.c',
   'resistance.c',
   'seat.c',

src/ssd/ssd_titlebar.c

@@ -53,7 +53,8 @@ ssd_titlebar_create(struct ssd *ssd)
 			corner_top_right = &theme->corner_top_right_inactive_normal->base;
 			menu_button_unpressed = &theme->button_menu_inactive_unpressed->base;
 			iconify_button_unpressed = &theme->button_iconify_inactive_unpressed->base;
-			maximize_button_unpressed = &theme->button_maximize_inactive_unpressed->base;
+			maximize_button_unpressed =
+				&theme->button_maximize_inactive_unpressed->base;
 			close_button_unpressed = &theme->button_close_inactive_unpressed->base;
 			wlr_scene_node_set_enabled(&parent->node, false);
 		}

src/theme.c

@@ -24,6 +24,7 @@
 #include "common/match.h"
 #include "common/string-helpers.h"
 #include "config/rcxml.h"
+#include "button-png.h"
 #include "theme.h"
 #include "xbm/xbm.h"
 #include "buffer.h"
@@ -95,9 +96,23 @@ load_buttons(struct theme *theme)
 	char filename[4096] = {0};
 	for (size_t i = 0; i < sizeof(buttons) / sizeof(buttons[0]); ++i) {
 		struct button *b = &buttons[i];
+
+		/* Try png icon first */
+		snprintf(filename, sizeof(filename), "%s-active.png", b->name);
+		png_load(filename, b->active.buffer);
+		snprintf(filename, sizeof(filename), "%s-inactive.png", b->name);
+		png_load(filename, b->inactive.buffer);
+
+		/* If there were no png buttons, use xbm */
 		snprintf(filename, sizeof(filename), "%s.xbm", b->name);
-		xbm_load_button(filename, b->active.buffer, b->fallback_button, b->active.rgba);
-		xbm_load_button(filename, b->inactive.buffer, b->fallback_button, b->inactive.rgba);
+		if (!*b->active.buffer) {
+			xbm_load_button(filename, b->active.buffer,
+				b->fallback_button, b->active.rgba);
+		}
+		if (!*b->inactive.buffer) {
+			xbm_load_button(filename, b->inactive.buffer,
+				b->fallback_button, b->inactive.rgba);
+		}
 	}
 }