cycle: implement scrollable OSD

Before this commit, the OSD could overflow the screen when displaying
many window items. In this commit, we hide the overflowed items and
show a scrollbar to fit the OSD within the screen.

include/cycle.h

@@ -8,6 +8,7 @@
 #include "config/types.h"
 
 struct output;
+struct wlr_box;
 
 enum lab_cycle_dir {
 	LAB_CYCLE_DIR_NONE,
@@ -67,8 +68,21 @@ struct cycle_osd_output {
 	struct output *output;
 	struct wl_listener tree_destroy;
 
+	/* set by cycle_osd_impl->init() */
 	struct wl_list items; /* struct cycle_osd_item.link */
 	struct wlr_scene_tree *tree;
+	/* set by cycle_osd_impl->init() and moved by cycle_osd_scroll_update() */
+	struct wlr_scene_tree *items_tree;
+
+	/* used in osd-scroll.c */
+	struct cycle_osd_scroll_context {
+		int top_row_idx;
+		int nr_rows, nr_cols, nr_visible_rows;
+		int delta_y;
+		struct wlr_box bar_area;
+		struct wlr_scene_tree *bar_tree;
+		struct lab_scene_rect *bar;
+	} scroll;
 };
 
 struct buf;
@@ -124,6 +138,28 @@ struct cycle_osd_impl {
 	void (*update)(struct cycle_osd_output *osd_output);
 };
 
+#define SCROLLBAR_W 10
+
+/**
+ * Initialize the context and scene for scrolling OSD items.
+ *
+ * @output: Output of the OSD
+ * @bar_area: Area where the scrollbar is drawn
+ * @delta_y: The vertical delta by which items are scrolled (usually item height)
+ * @nr_cols: Number of columns in the OSD
+ * @nr_rows: Number of rows in the OSD
+ * @nr_visible_rows: Number of visible rows in the OSD
+ * @border_color: Border color of the scrollbar
+ * @bg_color: Background color of the scrollbar
+ */
+void cycle_osd_scroll_init(struct cycle_osd_output *osd_output,
+	struct wlr_box bar_area, int delta_y,
+	int nr_cols, int nr_rows, int nr_visible_rows,
+	float *border_color, float *bg_color);
+
+/* Scroll the OSD to show server->cycle.selected_view if needed */
+void cycle_osd_scroll_update(struct cycle_osd_output *osd_output);
+
 extern struct cycle_osd_impl cycle_osd_classic_impl;
 extern struct cycle_osd_impl cycle_osd_thumbnail_impl;
 

src/cycle/meson.build

@@ -2,5 +2,6 @@ labwc_sources += files(
   'cycle.c',
   'osd-classic.c',
   'osd-field.c',
+  'osd-scroll.c',
   'osd-thumbnail.c',
 )

src/cycle/osd-classic.c

@@ -97,11 +97,16 @@ cycle_osd_classic_init(struct cycle_osd_output *osd_output)
 	if (switcher_theme->width_is_percent) {
 		w = output_box.width * switcher_theme->width / 100;
 	}
-	int h = nr_views * switcher_theme->item_height + 2 * padding;
+	int workspace_name_h = 0;
 	if (show_workspace) {
 		/* workspace indicator */
-		h += switcher_theme->item_height;
+		workspace_name_h = switcher_theme->item_height;
 	}
+	int nr_visible_views = (output_box.height - workspace_name_h - 2 * padding)
+				/ switcher_theme->item_height;
+	nr_visible_views = MIN(nr_visible_views, nr_views);
+	int h = workspace_name_h + nr_visible_views * switcher_theme->item_height
+		+ 2 * padding;
 
 	osd_output->tree = wlr_scene_tree_create(output->cycle_osd_tree);
 
@@ -154,13 +159,17 @@ cycle_osd_classic_init(struct cycle_osd_output *osd_output)
 		goto error;
 	}
 
+	float *active_bg_color = switcher_theme->item_active_bg_color;
+	float *active_border_color = switcher_theme->item_active_border_color;
+	osd_output->items_tree = wlr_scene_tree_create(osd_output->tree);
+
 	/* Draw text for each node */
 	struct view *view;
 	wl_list_for_each(view, &server->cycle.views, cycle_link) {
 		struct cycle_osd_classic_item *item = znew(*item);
 		wl_list_append(&osd_output->items, &item->base.link);
 		item->base.view = view;
-		item->base.tree = wlr_scene_tree_create(osd_output->tree);
+		item->base.tree = wlr_scene_tree_create(osd_output->items_tree);
 		node_descriptor_create(&item->base.tree->node,
 			LAB_NODE_CYCLE_OSD_ITEM, NULL, item);
 		/*
@@ -186,9 +195,6 @@ cycle_osd_classic_init(struct cycle_osd_output *osd_output)
 		item->active_tree = wlr_scene_tree_create(item->base.tree);
 		wlr_scene_node_set_enabled(&item->active_tree->node, false);
 
-		float *active_bg_color = switcher_theme->item_active_bg_color;
-		float *active_border_color = switcher_theme->item_active_border_color;
-
 		/* Highlight around selected window's item */
 		struct lab_scene_rect_options highlight_opts = {
 			.border_colors = (float *[1]) {active_border_color},
@@ -215,6 +221,17 @@ cycle_osd_classic_init(struct cycle_osd_output *osd_output)
 		y += switcher_theme->item_height;
 	}
 
+	struct wlr_box scrollbar_area = {
+		.x = w - padding - SCROLLBAR_W,
+		.y = padding,
+		.width = SCROLLBAR_W,
+		.height = h - 2 * padding,
+	};
+	cycle_osd_scroll_init(osd_output, scrollbar_area,
+		switcher_theme->item_height,
+		/*nr_cols*/ 1, /*nr_rows*/ nr_views, nr_visible_views,
+		active_border_color, active_bg_color);
+
 error:;
 	/* Center OSD */
 	wlr_scene_node_set_position(&osd_output->tree->node,
@@ -226,6 +243,8 @@ static void
 cycle_osd_classic_update(struct cycle_osd_output *osd_output)
 {
 	struct server *server = osd_output->output->server;
+	cycle_osd_scroll_update(osd_output);
+
 	struct cycle_osd_classic_item *item;
 	wl_list_for_each(item, &osd_output->items, base.link) {
 		bool active = item->base.view == server->cycle.selected_view;

src/cycle/osd-scroll.c

@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <assert.h>
+#include <wlr/types/wlr_scene.h>
+#include "common/lab-scene-rect.h"
+#include "labwc.h"
+#include "cycle.h"
+#include "output.h"
+
+void
+cycle_osd_scroll_init(struct cycle_osd_output *osd_output, struct wlr_box bar_area,
+		int delta_y, int nr_cols, int nr_rows, int nr_visible_rows,
+		float *border_color, float *bg_color)
+{
+	if (nr_visible_rows >= nr_rows) {
+		/* OSD doesn't have so many windows to scroll through */
+		return;
+	}
+
+	struct cycle_osd_scroll_context *scroll = &osd_output->scroll;
+	scroll->nr_cols = nr_cols;
+	scroll->nr_rows = nr_rows;
+	scroll->nr_visible_rows = nr_visible_rows;
+	scroll->top_row_idx = 0;
+	scroll->bar_area = bar_area;
+	scroll->delta_y = delta_y;
+	scroll->bar_tree = wlr_scene_tree_create(osd_output->tree);
+	wlr_scene_node_set_position(&scroll->bar_tree->node,
+		bar_area.x, bar_area.y);
+
+	struct lab_scene_rect_options scrollbar_opts = {
+		.border_colors = (float *[1]) { border_color },
+		.nr_borders = 1,
+		.border_width = 1,
+		.bg_color = bg_color,
+		.width = bar_area.width,
+		.height = bar_area.height * nr_visible_rows / nr_rows,
+	};
+	scroll->bar = lab_scene_rect_create(scroll->bar_tree, &scrollbar_opts);
+}
+
+static int
+get_cycle_idx(struct cycle_osd_output *osd_output)
+{
+	struct server *server = osd_output->output->server;
+
+	int idx = 0;
+	struct cycle_osd_item *item;
+	wl_list_for_each(item, &osd_output->items, link) {
+		if (item->view == server->cycle.selected_view) {
+			return idx;
+		}
+		idx++;
+	}
+	assert(false && "selected view not found in items");
+	return -1;
+}
+
+void
+cycle_osd_scroll_update(struct cycle_osd_output *osd_output)
+{
+	struct cycle_osd_scroll_context *scroll = &osd_output->scroll;
+	if (!scroll->bar) {
+		return;
+	}
+
+	int cycle_idx = get_cycle_idx(osd_output);
+
+	/* Update the range of visible rows */
+	int bottom_row_idx = scroll->top_row_idx + scroll->nr_visible_rows;
+	while (cycle_idx < scroll->top_row_idx * scroll->nr_cols) {
+		scroll->top_row_idx--;
+		bottom_row_idx--;
+	}
+	while (cycle_idx >= bottom_row_idx * scroll->nr_cols) {
+		scroll->top_row_idx++;
+		bottom_row_idx++;
+	}
+
+	/* Vertically move scrollbar by (bar height) / (# of total rows) */
+	wlr_scene_node_set_position(&scroll->bar->tree->node, 0,
+		scroll->bar_area.height * scroll->top_row_idx / scroll->nr_rows);
+	/* Vertically move items */
+	wlr_scene_node_set_position(&osd_output->items_tree->node, 0,
+		-scroll->delta_y * scroll->top_row_idx);
+
+	/* Hide items outside of visible area */
+	int idx = 0;
+	struct cycle_osd_item *item;
+	wl_list_for_each(item, &osd_output->items, link) {
+		bool visible = idx >= scroll->top_row_idx * scroll->nr_cols
+			&& idx < bottom_row_idx * scroll->nr_cols;
+		wlr_scene_node_set_enabled(&item->tree->node, visible);
+		idx++;
+	}
+}

src/cycle/osd-thumbnail.c

@@ -194,9 +194,10 @@ create_item_scene(struct wlr_scene_tree *parent, struct view *view,
 }
 
 static void
-get_items_geometry(struct output *output, struct theme *theme,
+get_items_geometry(struct output *output, int nr_thumbs,
-		int nr_thumbs, int *nr_rows, int *nr_cols)
+		int *nr_cols, int *nr_rows, int *nr_visible_rows)
 {
+	struct theme *theme = output->server->theme;
 	struct window_switcher_thumbnail_theme *switcher_theme =
 		&theme->osd_window_switcher_thumbnail;
 	int output_width, output_height;
@@ -223,6 +224,9 @@ get_items_geometry(struct output *output, struct theme *theme,
 		(*nr_rows)++;
 		*nr_cols = ceilf((float)nr_thumbs / *nr_rows);
 	}
+
+	*nr_visible_rows = MIN(*nr_rows,
+		(output_height - 2 * padding) / switcher_theme->item_height);
 }
 
 static void
@@ -236,18 +240,19 @@ cycle_osd_thumbnail_init(struct cycle_osd_output *osd_output)
 	int padding = theme->osd_border_width + switcher_theme->padding;
 
 	osd_output->tree = wlr_scene_tree_create(output->cycle_osd_tree);
+	osd_output->items_tree = wlr_scene_tree_create(osd_output->tree);
 
 	int nr_views = wl_list_length(&server->cycle.views);
 	assert(nr_views > 0);
-	int nr_rows, nr_cols;
+	int nr_cols, nr_rows, nr_visible_rows;
-	get_items_geometry(output, theme, nr_views, &nr_rows, &nr_cols);
+	get_items_geometry(output, nr_views, &nr_cols, &nr_rows, &nr_visible_rows);
 
 	/* items */
 	struct view *view;
 	int index = 0;
 	wl_list_for_each(view, &server->cycle.views, cycle_link) {
 		struct cycle_osd_thumbnail_item *item = create_item_scene(
-			osd_output->tree, view, osd_output);
+			osd_output->items_tree, view, osd_output);
 		if (!item) {
 			break;
 		}
@@ -257,14 +262,28 @@ cycle_osd_thumbnail_init(struct cycle_osd_output *osd_output)
 		index++;
 	}
 
+	int items_width = switcher_theme->item_width * nr_cols;
+	int items_height = switcher_theme->item_height * nr_visible_rows;
+
+	struct wlr_box scrollbar_area = {
+		.x = padding + items_width - SCROLLBAR_W,
+		.y = padding,
+		.width = SCROLLBAR_W,
+		.height = items_height,
+	};
+	cycle_osd_scroll_init(osd_output, scrollbar_area,
+		switcher_theme->item_height, nr_cols, nr_rows, nr_visible_rows,
+		switcher_theme->item_active_border_color,
+		switcher_theme->item_active_bg_color);
+
 	/* background */
 	struct lab_scene_rect_options bg_opts = {
 		.border_colors = (float *[1]) { theme->osd_border_color },
 		.nr_borders = 1,
 		.border_width = theme->osd_border_width,
 		.bg_color = theme->osd_bg_color,
-		.width = nr_cols * switcher_theme->item_width + 2 * padding,
+		.width = items_width + 2 * padding,
-		.height = nr_rows * switcher_theme->item_height + 2 * padding,
+		.height = items_height + 2 * padding,
 	};
 	struct lab_scene_rect *bg =
 		lab_scene_rect_create(osd_output->tree, &bg_opts);
@@ -283,6 +302,8 @@ static void
 cycle_osd_thumbnail_update(struct cycle_osd_output *osd_output)
 {
 	struct server *server = osd_output->output->server;
+	cycle_osd_scroll_update(osd_output);
+
 	struct cycle_osd_thumbnail_item *item;
 	wl_list_for_each(item, &osd_output->items, base.link) {
 		bool active = (item->base.view == server->cycle.selected_view);