i3 - improved tiling WM

Return DRAG_ABORT on UnmapNotify from drag_pointer

Patch status: needinfo

Patch by Tony Crisci

Long description:

Add DRAG_ABORT to enum drag_result_t. DRAG_ABORT will indicate the drag
operation cannot be completed.

Return DRAG_ABORT on UnmapNotify, or when the keyboard or pointer cannot
be grabbed.

Add DRAGGING to return value for drag_result_t. DRAGGING is used
internally by drag_pointer to indicate the drag is in progress.

Fixes an issue that caused i3 to crash when a user is dragging or
resizing a floating window that becomes destroyed.

To apply this patch, use:
curl http://cr.i3wm.org/patch/291/raw.patch | git am

b/include/floating.h

25 
@@ -134,12 +134,25 @@ void floating_toggle_hide(xcb_connection_t *conn, Workspace *workspace);
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 #endif
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 /**
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- * This is the return value of a drag operation like drag_pointer. DRAG_CANCEL
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- * will indicate the intention of the drag should not be carried out, or that
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- * the drag actions should be undone.
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+ * This is the return value of a drag operation like drag_pointer.
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+ *
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+ * DRAG_SUCCESS will indicate the intention of the drag action should be
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+ * carried out.
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+ *
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+ * DRAG_CANCEL will indicate that the drag was stopped by a user action, and an
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+ * attempt should be made to restore the state of the involved windows to their
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+ * condition before the drag.
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+ *
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+ * DRAG_ABORT will indicate that the intention of the drag action cannot be
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+ * carried out (e.g. because the window has been unmapped).
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  *
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  */
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-typedef enum { DRAG_SUCCESS = 0, DRAG_CANCEL } drag_result_t;
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+typedef enum {
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+    DRAGGING = 0,
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+    DRAG_SUCCESS,
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+    DRAG_CANCEL,
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+    DRAG_ABORT
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+} drag_result_t;
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 /**
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  * This function grabs your pointer and keyboard and lets you drag stuff around

b/src/floating.c

59 
@@ -601,7 +601,7 @@ drag_result_t drag_pointer(Con *con, const xcb_button_press_event_t *event, xcb_
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     if ((reply = xcb_grab_pointer_reply(conn, cookie, NULL)) == NULL) {
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         ELOG("Could not grab pointer\n");
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-        return DRAG_CANCEL;
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+        return DRAG_ABORT;
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     }
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     free(reply);
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@@ -620,7 +620,7 @@ drag_result_t drag_pointer(Con *con, const xcb_button_press_event_t *event, xcb_
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     if ((keyb_reply = xcb_grab_keyboard_reply(conn, keyb_cookie, NULL)) == NULL) {
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         ELOG("Could not grab keyboard\n");
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-        return DRAG_CANCEL;
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+        return DRAG_ABORT;
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     }
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     free(keyb_reply);
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@@ -629,11 +629,11 @@ drag_result_t drag_pointer(Con *con, const xcb_button_press_event_t *event, xcb_
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     xcb_flush(conn);
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     xcb_generic_event_t *inside_event, *last_motion_notify = NULL;
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-    bool loop_done = false;
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-    /* The return value, set to DRAG_CANCEL on user cancel */
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-    drag_result_t drag_result = DRAG_SUCCESS;
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+    Con *inside_con = NULL;
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+    /* The return value, set to exit the event loop */
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+    drag_result_t drag_result = DRAGGING;
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     /* I’ve always wanted to have my own eventhandler… */
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-    while (!loop_done && (inside_event = xcb_wait_for_event(conn))) {
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+    while (drag_result == DRAGGING && (inside_event = xcb_wait_for_event(conn))) {
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         /* We now handle all events we can get using xcb_poll_for_event */
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         do {
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             /* skip x11 errors */
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@@ -646,7 +646,7 @@ drag_result_t drag_pointer(Con *con, const xcb_button_press_event_t *event, xcb_
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             switch (type) {
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                 case XCB_BUTTON_RELEASE:
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-                    loop_done = true;
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+                    drag_result = DRAG_SUCCESS;
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                     break;
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                 case XCB_MOTION_NOTIFY:
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@@ -656,16 +656,18 @@ drag_result_t drag_pointer(Con *con, const xcb_button_press_event_t *event, xcb_
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                     break;
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                 case XCB_UNMAP_NOTIFY:
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-                    DLOG("Unmap-notify, aborting\n");
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+                    inside_con = con_by_window_id(((xcb_unmap_notify_event_t*)inside_event)->window);
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+
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+                    DLOG("UnmapNotify for window 0x%08x (container %p)\n", ((xcb_unmap_notify_event_t*)inside_event)->window, inside_con);
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+                    DLOG("UnmapNotify, aborting\n");
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+                    drag_result = DRAG_ABORT;
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+
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                     handle_event(type, inside_event);
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-                    loop_done = true;
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-                    drag_result = DRAG_CANCEL;
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                     break;
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                 case XCB_KEY_PRESS:
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                     /* Cancel the drag if a key was pressed */
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                     DLOG("A key was pressed during drag, canceling.");
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-                    loop_done = true;
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                     drag_result = DRAG_CANCEL;
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                     handle_event(type, inside_event);
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@@ -681,7 +683,7 @@ drag_result_t drag_pointer(Con *con, const xcb_button_press_event_t *event, xcb_
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                 free(inside_event);
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         } while ((inside_event = xcb_poll_for_event(conn)) != NULL);
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-        if (last_motion_notify == NULL || loop_done)
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+        if (last_motion_notify == NULL || drag_result != DRAGGING)
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             continue;
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         new_x = ((xcb_motion_notify_event_t*)last_motion_notify)->root_x;