[gnome-shell] screenshot: Promisify SelectArea

[Florian Müllner <fmuellner src gnome org>]

commit 9db62236da5021b0f4cd062fe3d3e9a39f64c4b7
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Dec 19 03:39:39 2019 +0100

    screenshot: Promisify SelectArea
    
    The screenshot code has a fair bit of nested callbacks, which means
    that it is a good use case for async functions and Promises.
    
    Most code uses GIO's async pattern, which means it can be easily turned
    into promises with Gio._promisify(); first handle the couple of cases
    that need custom code though, starting with SelectArea.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/903

 js/ui/screenshot.js | 59 ++++++++++++++++++++++++-----------------------------
 1 file changed, 27 insertions(+), 32 deletions(-)
---
diff --git a/js/ui/screenshot.js b/js/ui/screenshot.js
index fab8ed7e4f..e2526ebdb9 100644
--- a/js/ui/screenshot.js
+++ b/js/ui/screenshot.js
@@ -227,20 +227,19 @@ var ScreenshotService = class {
             });
     }
 
-    SelectAreaAsync(params, invocation) {
+    async SelectAreaAsync(params, invocation) {
         let selectArea = new SelectArea();
-        selectArea.show();
-        selectArea.connect('finished', (o, areaRectangle) => {
-            if (areaRectangle) {
-                let retRectangle = this._unscaleArea(areaRectangle.x, areaRectangle.y,
-                                                     areaRectangle.width, areaRectangle.height);
-                let retval = GLib.Variant.new('(iiii)', retRectangle);
-                invocation.return_value(retval);
-            } else {
-                invocation.return_error_literal(Gio.IOErrorEnum, Gio.IOErrorEnum.CANCELLED,
-                                                "Operation was cancelled");
-            }
-        });
+        try {
+            let areaRectangle = await selectArea.selectAsync();
+            let retRectangle = this._unscaleArea(
+                areaRectangle.x, areaRectangle.y,
+                areaRectangle.width, areaRectangle.height);
+            invocation.return_value(GLib.Variant.new('(iiii)', retRectangle));
+        } catch (e) {
+            invocation.return_error_literal(
+                Gio.IOErrorEnum, Gio.IOErrorEnum.CANCELLED,
+                'Operation was cancelled');
+        }
     }
 
     FlashAreaAsync(params, invocation) {
@@ -286,9 +285,8 @@ var ScreenshotService = class {
     }
 };
 
-var SelectArea = GObject.registerClass({
-    Signals: { 'finished': { param_types: [Meta.Rectangle.$gtype] } },
-}, class SelectArea extends St.Widget {
+var SelectArea = GObject.registerClass(
+class SelectArea extends St.Widget {
     _init() {
         this._startX = -1;
         this._startY = -1;
@@ -317,14 +315,21 @@ var SelectArea = GObject.registerClass({
         this.add_actor(this._rubberband);
     }
 
-    vfunc_show() {
-        if (!this._grabHelper.grab({ actor: this,
-                                     onUngrab: this._onUngrab.bind(this) }))
-            return;
-
+    async selectAsync() {
         global.display.set_cursor(Meta.Cursor.CROSSHAIR);
         Main.uiGroup.set_child_above_sibling(this, null);
-        super.vfunc_show();
+        this.show();
+
+        await this._grabHelper.grabAsync({ actor: this });
+
+        global.display.set_cursor(Meta.Cursor.DEFAULT);
+
+        GLib.idle_add(GLib.PRIORITY_DEFAULT, () => {
+            this.destroy();
+            return GLib.SOURCE_REMOVE;
+        });
+
+        return this._result;
     }
 
     _getGeometry() {
@@ -371,16 +376,6 @@ var SelectArea = GObject.registerClass({
         });
         return Clutter.EVENT_PROPAGATE;
     }
-
-    _onUngrab() {
-        global.display.set_cursor(Meta.Cursor.DEFAULT);
-        this.emit('finished', this._result);
-
-        GLib.idle_add(GLib.PRIORITY_DEFAULT, () => {
-            this.destroy();
-            return GLib.SOURCE_REMOVE;
-        });
-    }
 });
 
 var PickPixel = GObject.registerClass({