desktop-shell: Keep windows on screen when moving

We add a primitive constraining function to at least prevent users from
moving the window up under the panel.

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=73421

diff --git a/desktop-shell/shell.c b/desktop-shell/shell.c
index 690a3be..43b93f6 100644 (file)
--- a/desktop-shell/shell.c
+++ b/desktop-shell/shell.c
@@ -170,6 +170,10 @@ struct shell_surface {
        bool state_changed;
        bool state_requested;
 
+       struct {
+               int left, right, top, bottom;
+       } margin;
+
        int focus_count;
 };
 
@@ -189,6 +193,7 @@ struct shell_touch_grab {
 struct weston_move_grab {
        struct shell_grab base;
        wl_fixed_t dx, dy;
+       int client_initiated;
 };
 
 struct weston_touch_move_grab {
@@ -248,6 +253,10 @@ shell_fade_startup(struct desktop_shell *shell);
 static struct shell_seat *
 get_shell_seat(struct weston_seat *seat);
 
+static int
+get_output_panel_height(struct desktop_shell *shell,
+                       struct weston_output *output);
+
 static void
 shell_surface_update_child_surface_layers(struct shell_surface *shsurf);
 
@@ -1462,22 +1471,47 @@ noop_grab_focus(struct weston_pointer_grab *grab)
 }
 
 static void
+constrain_position(struct weston_move_grab *move, int *cx, int *cy)
+{
+       struct shell_surface *shsurf = move->base.shsurf;
+       struct weston_pointer *pointer = move->base.grab.pointer;
+       int x, y, panel_height, bottom, left, right;
+       const int safety = 50;
+
+       x = wl_fixed_to_int(pointer->x + move->dx);
+       y = wl_fixed_to_int(pointer->y + move->dy);
+
+       panel_height = get_output_panel_height(shsurf->shell,
+                                              shsurf->surface->output);
+       bottom = y + shsurf->surface->height - shsurf->margin.bottom;
+       if (bottom - panel_height < safety)
+               y = panel_height + safety -
+                       shsurf->surface->height + shsurf->margin.bottom;
+
+       if (move->client_initiated &&
+           y + shsurf->margin.top < panel_height)
+               y = panel_height - shsurf->margin.top;
+
+       *cx = x;
+       *cy = y;
+}
+
+static void
 move_grab_motion(struct weston_pointer_grab *grab, uint32_t time,
                 wl_fixed_t x, wl_fixed_t y)
 {
        struct weston_move_grab *move = (struct weston_move_grab *) grab;
        struct weston_pointer *pointer = grab->pointer;
        struct shell_surface *shsurf = move->base.shsurf;
-       int dx, dy;
+       int cx, cy;
 
        weston_pointer_move(pointer, x, y);
-       dx = wl_fixed_to_int(pointer->x + move->dx);
-       dy = wl_fixed_to_int(pointer->y + move->dy);
-
        if (!shsurf)
                return;
 
-       weston_view_set_position(shsurf->view, dx, dy);
+       constrain_position(move, &cx, &cy);
+
+       weston_view_set_position(shsurf->view, cx, cy);
 
        weston_compositor_schedule_repaint(shsurf->surface->compositor);
 }
@@ -1516,7 +1550,8 @@ static const struct weston_pointer_grab_interface move_grab_interface = {
 };
 
 static int
-surface_move(struct shell_surface *shsurf, struct weston_seat *seat)
+surface_move(struct shell_surface *shsurf, struct weston_seat *seat,
+            int client_initiated)
 {
        struct weston_move_grab *move;
 
@@ -1534,6 +1569,7 @@ surface_move(struct shell_surface *shsurf, struct weston_seat *seat)
                        seat->pointer->grab_x;
        move->dy = wl_fixed_from_double(shsurf->view->geometry.y) -
                        seat->pointer->grab_y;
+       move->client_initiated = client_initiated;
 
        shell_grab_start(&move->base, &move_grab_interface, shsurf,
                         seat->pointer, DESKTOP_SHELL_CURSOR_MOVE);
@@ -1558,7 +1594,7 @@ common_surface_move(struct wl_resource *resource,
            seat->pointer->grab_serial == serial) {
                surface = weston_surface_get_main_surface(seat->pointer->focus->surface);
                if ((surface == shsurf->surface) &&
-                   (surface_move(shsurf, seat) < 0))
+                   (surface_move(shsurf, seat, 1) < 0))
                        wl_resource_post_no_memory(resource);
        } else if (seat->touch &&
                   seat->touch->focus &&
@@ -1804,7 +1840,7 @@ busy_cursor_grab_button(struct weston_pointer_grab *base,
 
        if (shsurf && button == BTN_LEFT && state) {
                activate(shsurf->shell, shsurf->surface, seat);
-               surface_move(shsurf, seat);
+               surface_move(shsurf, seat, 0);
        } else if (shsurf && button == BTN_RIGHT && state) {
                activate(shsurf->shell, shsurf->surface, seat);
                surface_rotate(shsurf, seat);
@@ -2780,6 +2816,12 @@ set_xwayland(struct shell_surface *shsurf, int x, int y, uint32_t flags)
        shsurf->state_changed = true;
 }
 
+static int
+shell_interface_move(struct shell_surface *shsurf, struct weston_seat *ws)
+{
+       return surface_move(shsurf, ws, 1);
+}
+
 static const struct weston_pointer_grab_interface popup_grab_interface;
 
 static void
@@ -3298,8 +3340,12 @@ xdg_surface_set_margin(struct wl_client *client,
                             int32_t top,
                             int32_t bottom)
 {
-       /* Do nothing, Weston doesn't try to constrain or place
-        * surfaces in any special manner... */
+       struct shell_surface *shsurf = wl_resource_get_user_data(resource);
+
+       shsurf->margin.left = left;
+       shsurf->margin.right = right;
+       shsurf->margin.top = top;
+       shsurf->margin.bottom = bottom;
 }
 
 static void
@@ -4017,7 +4063,7 @@ move_binding(struct weston_seat *seat, uint32_t time, uint32_t button, void *dat
            shsurf->state.maximized)
                return;
 
-       surface_move(shsurf, (struct weston_seat *) seat);
+       surface_move(shsurf, (struct weston_seat *) seat, 0);
 }
 
 static void
@@ -6024,7 +6070,7 @@ module_init(struct weston_compositor *ec,
        ec->shell_interface.set_transient = set_transient;
        ec->shell_interface.set_fullscreen = set_fullscreen;
        ec->shell_interface.set_xwayland = set_xwayland;
-       ec->shell_interface.move = surface_move;
+       ec->shell_interface.move = shell_interface_move;
        ec->shell_interface.resize = surface_resize;
        ec->shell_interface.set_title = set_title;