Implement title alignment

This adds support for `i3 4.16`'s ability to set the title alignment.
The command is `title_align left|center|right`.

When the title is on the right, marks are moved to the left. Otherwise,
they are on the right.

8 files changed, 126 insertions, 21 deletions

diff --git a/include/sway/commands.h b/include/sway/commands.h
index e6036e51..eb446eae 100644
--- a/include/sway/commands.h
+++ b/include/sway/commands.h
@@ -172,6 +172,7 @@ sway_cmd cmd_swaybg_command;
 sway_cmd cmd_swaynag_command;
 sway_cmd cmd_swap;
 sway_cmd cmd_tiling_drag;
+sway_cmd cmd_title_align;
 sway_cmd cmd_title_format;
 sway_cmd cmd_titlebar_border_thickness;
 sway_cmd cmd_titlebar_padding;
diff --git a/include/sway/config.h b/include/sway/config.h
index a6920835..1ff9a104 100644
--- a/include/sway/config.h
+++ b/include/sway/config.h
@@ -357,6 +357,12 @@ enum mouse_warping_mode {
 	WARP_CONTAINER
 };
 
+enum alignment {
+	ALIGN_LEFT,
+	ALIGN_CENTER,
+	ALIGN_RIGHT
+};
+
 /**
  * The configuration struct. The result of loading a config file.
  */
@@ -409,6 +415,7 @@ struct sway_config {
 	bool validating;
 	bool auto_back_and_forth;
 	bool show_marks;
+	enum alignment title_align;
 	bool tiling_drag;
 
 	bool smart_gaps;
diff --git a/sway/commands.c b/sway/commands.c
index d35658d5..bffc18f6 100644
--- a/sway/commands.c
+++ b/sway/commands.c
@@ -103,6 +103,7 @@ static struct cmd_handler handlers[] = {
 	{ "smart_borders", cmd_smart_borders },
 	{ "smart_gaps", cmd_smart_gaps },
 	{ "tiling_drag", cmd_tiling_drag },
+	{ "title_align", cmd_title_align },
 	{ "titlebar_border_thickness", cmd_titlebar_border_thickness },
 	{ "titlebar_padding", cmd_titlebar_padding },
 	{ "workspace", cmd_workspace },
diff --git a/sway/commands/title_align.c b/sway/commands/title_align.c
new file mode 100644
index 00000000..82578186
--- /dev/null
+++ b/sway/commands/title_align.c
@@ -0,0 +1,30 @@
+#include "sway/commands.h"
+#include "sway/config.h"
+#include "sway/output.h"
+#include "sway/tree/container.h"
+#include "sway/tree/root.h"
+
+struct cmd_results *cmd_title_align(int argc, char **argv) {
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, "title_align", EXPECTED_AT_LEAST, 1))) {
+		return error;
+	}
+
+	if (strcmp(argv[0], "left") == 0) {
+		config->title_align = ALIGN_LEFT;
+	} else if (strcmp(argv[0], "center") == 0) {
+		config->title_align = ALIGN_CENTER;
+	} else if (strcmp(argv[0], "right") == 0) {
+		config->title_align = ALIGN_RIGHT;
+	} else {
+		return cmd_results_new(CMD_INVALID, "title_align",
+				"Expected 'title_align left|center|right'");
+	}
+
+	for (int i = 0; i < root->outputs->length; ++i) {
+		struct sway_output *output = root->outputs->items[i];
+		output_damage_whole(output);
+	}
+
+	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+}
diff --git a/sway/config.c b/sway/config.c
index 59edc6d8..675d20e5 100644
--- a/sway/config.c
+++ b/sway/config.c
@@ -234,6 +234,7 @@ static void config_defaults(struct sway_config *config) {
 	config->auto_back_and_forth = false;
 	config->reading = false;
 	config->show_marks = true;
+	config->title_align = ALIGN_LEFT;
 	config->tiling_drag = true;
 
 	config->smart_gaps = false;
diff --git a/sway/desktop/render.c b/sway/desktop/render.c
index 51cb8980..eeda496c 100644
--- a/sway/desktop/render.c
+++ b/sway/desktop/render.c
@@ -371,6 +371,7 @@ static void render_titlebar(struct sway_output *output,
 	int titlebar_border_thickness = config->titlebar_border_thickness;
 	int titlebar_h_padding = config->titlebar_h_padding;
 	int titlebar_v_padding = config->titlebar_v_padding;
+	enum alignment title_align = config->title_align;
 
 	// Single pixel bar above title
 	memcpy(&color, colors->border, sizeof(float) * 4);
@@ -420,19 +421,25 @@ static void render_titlebar(struct sway_output *output,
 		render_rect(output->wlr_output, output_damage, &box, color);
 	}
 
-	size_t inner_width = width - titlebar_h_padding * 2;
+	int inner_x = x - output_x + titlebar_h_padding;
 	int bg_y = y + titlebar_border_thickness;
+	size_t inner_width = width - titlebar_h_padding * 2;
+
+	// output-buffer local
+	int ob_inner_x = round(inner_x * output_scale);
+	int ob_inner_width = scale_length(inner_width, inner_x, output_scale);
 	int ob_bg_height = scale_length(
 			(titlebar_v_padding - titlebar_border_thickness) * 2 +
 			config->font_height, bg_y, output_scale);
 
 	// Marks
-	int marks_ob_width = 0; // output-buffer-local
+	int ob_marks_x = 0; // output-buffer-local
+	int ob_marks_width = 0; // output-buffer-local
 	if (config->show_marks && marks_texture) {
 		struct wlr_box texture_box;
 		wlr_texture_get_size(marks_texture,
 			&texture_box.width, &texture_box.height);
-		marks_ob_width = texture_box.width;
+		ob_marks_width = texture_box.width;
 
 		// The marks texture might be shorter than the config->font_height, in
 		// which case we need to pad it as evenly as possible above and below.
@@ -440,9 +447,15 @@ static void render_titlebar(struct sway_output *output,
 		int ob_padding_above = floor(ob_padding_total / 2.0);
 		int ob_padding_below = ceil(ob_padding_total / 2.0);
 
-		// Render texture
-		texture_box.x = round((x - output_x + width - titlebar_h_padding)
-				* output_scale) - texture_box.width;
+		// Render texture. If the title is on the right, the marks will be on
+		// the left. Otherwise, they will be on the right.
+		if (title_align == ALIGN_RIGHT || texture_box.width > ob_inner_width) {
+			texture_box.x = ob_inner_x;
+		} else {
+			texture_box.x = ob_inner_x + ob_inner_width - texture_box.width;
+		}
+		ob_marks_x = texture_box.x;
+
 		texture_box.y = round((bg_y - output_y) * output_scale) +
 			ob_padding_above;
 
@@ -451,8 +464,8 @@ static void render_titlebar(struct sway_output *output,
 			WL_OUTPUT_TRANSFORM_NORMAL,
 			0.0, output->wlr_output->transform_matrix);
 
-		if (inner_width * output_scale < texture_box.width) {
-			texture_box.width = inner_width * output_scale;
+		if (ob_inner_width < texture_box.width) {
+			texture_box.width = ob_inner_width;
 		}
 		render_texture(output->wlr_output, output_damage, marks_texture,
 			&texture_box, matrix, con->alpha);
@@ -473,12 +486,13 @@ static void render_titlebar(struct sway_output *output,
 	}
 
 	// Title text
-	size_t title_ob_width = 0; // output-buffer-local
+	int ob_title_x = 0;  // output-buffer-local
+	int ob_title_width = 0; // output-buffer-local
 	if (title_texture) {
 		struct wlr_box texture_box;
 		wlr_texture_get_size(title_texture,
 			&texture_box.width, &texture_box.height);
-		title_ob_width = texture_box.width;
+		ob_title_width = texture_box.width;
 
 		// The title texture might be shorter than the config->font_height,
 		// in which case we need to pad it above and below.
@@ -489,8 +503,26 @@ static void render_titlebar(struct sway_output *output,
 			texture_box.height;
 
 		// Render texture
-		texture_box.x =
-			round((x - output_x + titlebar_h_padding) * output_scale);
+		if (texture_box.width > ob_inner_width - ob_marks_width) {
+			texture_box.x = (title_align == ALIGN_RIGHT && ob_marks_width)
+				? ob_marks_x + ob_marks_width : ob_inner_x;
+		} else if (title_align == ALIGN_LEFT) {
+			texture_box.x = ob_inner_x;
+		} else if (title_align == ALIGN_CENTER) {
+			// If there are marks visible, center between the edge and marks.
+			// Otherwise, center in the inner area.
+			if (ob_marks_width) {
+				texture_box.x = (ob_inner_x + ob_marks_x) / 2
+					- texture_box.width / 2;
+			} else {
+				texture_box.x = ob_inner_x + ob_inner_width / 2
+					- texture_box.width / 2;
+			}
+		} else {
+			texture_box.x = ob_inner_x + ob_inner_width - texture_box.width;
+		}
+		ob_title_x = texture_box.x;
+
 		texture_box.y =
 			round((bg_y - output_y) * output_scale) + ob_padding_above;
 
@@ -499,11 +531,10 @@ static void render_titlebar(struct sway_output *output,
 			WL_OUTPUT_TRANSFORM_NORMAL,
 			0.0, output->wlr_output->transform_matrix);
 
-		int inner_x = x - output_x + titlebar_h_padding;
-		int ob_inner_width = scale_length(inner_width, inner_x, output_scale);
-		if (ob_inner_width - marks_ob_width < texture_box.width) {
-			texture_box.width = ob_inner_width - marks_ob_width;
+		if (ob_inner_width - ob_marks_width < texture_box.width) {
+			texture_box.width = ob_inner_width - ob_marks_width;
 		}
+
 		render_texture(output->wlr_output, output_damage, title_texture,
 			&texture_box, matrix, con->alpha);
 
@@ -522,17 +553,36 @@ static void render_titlebar(struct sway_output *output,
 		render_rect(output->wlr_output, output_damage, &box, color);
 	}
 
+	// Determine the left + right extends of the textures (output-buffer local)
+	int ob_left_x, ob_left_width, ob_right_x, ob_right_width;
+	if (ob_title_x < ob_marks_x) {
+		ob_left_x = ob_title_x;
+		ob_left_width = ob_title_width;
+		ob_right_x = ob_marks_x;
+		ob_right_width = ob_marks_width;
+	} else {
+		ob_left_x = ob_marks_x;
+		ob_left_width = ob_marks_width;
+		ob_right_x = ob_title_x;
+		ob_right_width = ob_title_width;
+	}
+	if (ob_left_x < ob_inner_x) {
+		ob_left_x = ob_inner_x;
+	} else if (ob_left_x + ob_left_width > ob_right_x + ob_right_width) {
+		ob_right_x = ob_left_x;
+		ob_right_width = ob_left_width;
+	}
+
 	// Filler between title and marks
-	box.width =
-		round(inner_width * output_scale) - title_ob_width - marks_ob_width;
+	box.width = ob_right_x - ob_left_x - ob_left_width;
 	if (box.width > 0) {
-		box.x = round((x + titlebar_h_padding) * output_scale) + title_ob_width;
+		box.x = ob_left_x + ob_left_width + round(output_x * output_scale);
 		box.y = round(bg_y * output_scale);
 		box.height = ob_bg_height;
 		render_rect(output->wlr_output, output_damage, &box, color);
 	}
 
-	// Padding left of title
+	// Padding on left side
 	left_offset = (layout == L_TABBED) * titlebar_border_thickness;
 	box.x = x + left_offset;
 	box.y = y + titlebar_border_thickness;
@@ -540,9 +590,13 @@ static void render_titlebar(struct sway_output *output,
 	box.height = (titlebar_v_padding - titlebar_border_thickness) * 2 +
 		config->font_height;
 	scale_box(&box, output_scale);
+	int left_x = ob_left_x + round(output_x * output_scale);
+	if (box.x + box.width < left_x) {
+		box.width += left_x - box.x - box.width;
+	}
 	render_rect(output->wlr_output, output_damage, &box, color);
 
-	// Padding right of marks
+	// Padding on right side
 	right_offset = (layout == L_TABBED) * titlebar_border_thickness;
 	box.x = x + width - titlebar_h_padding;
 	box.y = y + titlebar_border_thickness;
@@ -550,6 +604,11 @@ static void render_titlebar(struct sway_output *output,
 	box.height = (titlebar_v_padding - titlebar_border_thickness) * 2 +
 		config->font_height;
 	scale_box(&box, output_scale);
+	int right_rx = ob_right_x + ob_right_width + round(output_x * output_scale);
+	if (right_rx < box.x) {
+		box.width += box.x - right_rx;
+		box.x = right_rx;
+	}
 	render_rect(output->wlr_output, output_damage, &box, color);
 
 	if (connects_sides) {
diff --git a/sway/meson.build b/sway/meson.build
index c8c95a96..75131891 100644
--- a/sway/meson.build
+++ b/sway/meson.build
@@ -88,6 +88,7 @@ sway_sources = files(
 	'commands/swaynag_command.c',
 	'commands/swap.c',
 	'commands/tiling_drag.c',
+	'commands/title_align.c',
 	'commands/title_format.c',
 	'commands/titlebar_border_thickness.c',
 	'commands/titlebar_padding.c',
diff --git a/sway/sway.5.scd b/sway/sway.5.scd
index 6ccb1acf..4edd16bf 100644
--- a/sway/sway.5.scd
+++ b/sway/sway.5.scd
@@ -555,6 +555,11 @@ The default colors are:
 	Set the opacity of the window between 0 (completely transparent) and 1
 	(completely opaque).
 
+*title\_align* left|center|right
+	Sets the title alignment. If _right_ is selected and _show\_marks_ is set
+	to _yes_, the marks will be shown on the _left_ side instead of the
+	_right_ side.
+
 *unmark* [<identifier>]
 	*unmark* will remove _identifier_ from the list of current marks on a
 	window. If _identifier_ is omitted, all marks are removed.