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.