Add scaled_font_buffer implementation

include/common/scaled_font_buffer.h

@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __LAB_COMMON_SCALED_FONT_BUFFER_H
+#define __LAB_COMMON_SCALED_FONT_BUFFER_H
+
+struct font;
+struct wlr_scene_tree;
+struct wlr_scene_buffer;
+struct scaled_scene_buffere;
+
+struct scaled_font_buffer {
+	struct wlr_scene_buffer *scene_buffer;
+	int width;   /* unscaled, read only */
+	int height;  /* unscaled, read only */
+
+	/* Private */
+	char *text;
+	int max_width;
+	float color[4];
+	struct font font;
+	struct scaled_scene_buffer *scaled_buffer;
+};
+
+/**
+ * Create an auto scaling font buffer, providing a wlr_scene_buffer node for
+ * display. It gets destroyed automatically when the backing scaled_scene_buffer
+ * is being destoyed which in turn happens automatically when the backing
+ * wlr_scene_buffer (or one of its parents) is being destroyed.
+ *
+ * To actually show some text, scaled_font_buffer_update() has to be called.
+ *
+ */
+struct scaled_font_buffer *scaled_font_buffer_create(struct wlr_scene_tree *parent);
+
+/**
+ * Update an existing auto scaling font buffer.
+ *
+ * No steps are taken to detect if its actually required to render a new buffer.
+ * This should be done by the caller to prevent useless recreation of the same
+ * buffer in case nothing actually changed.
+ *
+ * Some basic checks could be something like
+ * - truncated = buffer->width == max_width
+ * - text_changed = strcmp(old_text, new_text)
+ * - font and color the same
+ */
+void scaled_font_buffer_update(struct scaled_font_buffer *self, const char *text,
+	int max_width, struct font *font, float *color);
+
+#endif /* __LAB_COMMON_SCALED_FONT_BUFFER_H */

src/common/meson.build

@@ -4,6 +4,7 @@ labwc_sources += files(
   'font.c',
   'grab-file.c',
   'nodename.c',
+  'scaled_font_buffer.c',
   'scaled_scene_buffer.c',
   'scene-helpers.c',
   'spawn.c',

src/common/scaled_font_buffer.c

@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#define _POSIX_C_SOURCE 200809L
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include <wayland-server-core.h>
+#include <wlr/util/log.h>
+#include "buffer.h"
+#include "common/font.h"
+#include "common/scaled_scene_buffer.h"
+#include "common/scaled_font_buffer.h"
+#include "common/zfree.h"
+
+static struct lab_data_buffer *
+_create_buffer(struct scaled_scene_buffer *scaled_buffer, double scale)
+{
+	struct lab_data_buffer *buffer;
+	struct scaled_font_buffer *self = scaled_buffer->data;
+
+	/* Buffer gets free'd automatically along the backing wlr_buffer */
+	font_buffer_create(&buffer, self->max_width, self->text,
+		&self->font, self->color, scale);
+
+	self->width = buffer ? buffer->unscaled_width : 0;
+	self->height = buffer ? buffer->unscaled_height : 0;
+	return buffer;
+}
+
+static void
+_destroy(struct scaled_scene_buffer *scaled_buffer)
+{
+	struct scaled_font_buffer *self = scaled_buffer->data;
+	if (self->text) {
+		zfree(self->text);
+	}
+	if (self->font.name) {
+		zfree(self->font.name);
+	}
+	zfree(scaled_buffer->data);
+}
+
+static const struct scaled_scene_buffer_impl impl = {
+	.create_buffer = _create_buffer,
+	.destroy = _destroy
+};
+
+/* Public API */
+struct scaled_font_buffer *
+scaled_font_buffer_create(struct wlr_scene_tree *parent)
+{
+	assert(parent);
+	struct scaled_font_buffer *self = calloc(1, sizeof(*self));
+	if (!self) {
+		return NULL;
+	}
+
+	struct scaled_scene_buffer *scaled_buffer
+		= scaled_scene_buffer_create(parent, &impl);
+	if (!scaled_buffer) {
+		free(self);
+		return NULL;
+	}
+
+	scaled_buffer->data = self;
+	self->scaled_buffer = scaled_buffer;
+	self->scene_buffer = scaled_buffer->scene_buffer;
+	return self;
+}
+
+void
+scaled_font_buffer_update(struct scaled_font_buffer *self,
+		const char *text, int max_width, struct font *font, float *color)
+{
+	assert(self);
+	assert(text);
+	assert(font);
+	assert(color);
+
+	/* Clean up old internal state */
+	if (self->text) {
+		zfree(self->text);
+	}
+	if (self->font.name) {
+		zfree(self->font.name);
+	}
+
+	/* Update internal state */
+	self->text = strdup(text);
+	self->max_width = max_width;
+	if (font->name) {
+		self->font.name = strdup(font->name);
+	}
+	self->font.size = font->size;
+	memcpy(self->color, color, sizeof(self->color));
+
+	/* Invalidate cache and force a new render */
+	scaled_scene_buffer_invalidate_cache(self->scaled_buffer);
+}