Use known width and height of the shell instead of asking

GDK.gdk_window_get_frame_extents (window, rect).

For GDK.gdk_window_get_frame_extents (window, rect) to return correct
values shell should be open. Once SWT asks GTK to show the shell via
Native calls it takes sometime to open the shell.
On high performance machines adjustTrip is asking GTK to give it width
and height before it has completely opened the shell. This results in
returning default size.(which is {0,0,1,1})
So We can use the height and width which we already know when opening
the shell.

 Fixes #1161

Author: raghucssit

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Shell.java

@@ -479,20 +479,45 @@ void addToolTip (ToolTip toolTip) {
 	toolTips = newToolTips;
 }
 
-void adjustTrim () {
+/**
+ * Resize the shell based on the trim width and height. Trim width and height
+ * adjustments are read from '$HOME/.swt/trims.prefs' for each trim style. If
+ * such a file does not exist then the trim values are queried from GTK.
+ *
+ * Note that we are trying to resize the shell which is already open. Shell
+ * already has width and height, Which is either set by setSize()/setBounds() or
+ * size is calculated based on layout and content of the shell. Without setting
+ * bounds/layout shell won't display content which is created on it.
+ *
+ * @param widthHint  Current width of the shell that is already open.
+ * @param heightHint Current height of the shell that is already open.
+ */
+void adjustTrim (int widthHint, int heightHint) {
 	if (display.ignoreTrim) return;
 	GtkAllocation allocation = new GtkAllocation ();
 	GTK.gtk_widget_get_allocation (shellHandle, allocation);
 	int width = allocation.width;
 	int height = allocation.height;
-	GdkRectangle rect = new GdkRectangle ();
 
+	//Ask Gtk for actual window frame extents
+	GdkRectangle rect = new GdkRectangle ();
 	if (!GTK.GTK4) {
 		long window = gtk_widget_get_window (shellHandle);
 		GDK.gdk_window_get_frame_extents (window, rect);
+
+		// Gtk returns default window dimensions as {0,0,1,1} if the window is not
+		// ready. If GTK returns window dimensions we can use it, if not, we will use
+		// "requested" shell size as returned by gtk_window_resize() in setVisible().
+		// See https://github.com/eclipse-platform/eclipse.platform.swt/issues/1161
+		if (rect.width > 1 || rect.height > 1) {
+			widthHint = rect.width;
+			heightHint = rect.height;
+		}
 	}
-	int trimWidth = Math.max (0, rect.width - width);
-	int trimHeight = Math.max (0, rect.height - height);
+
+
+	int trimWidth = Math.max (0, widthHint - width);
+	int trimHeight = Math.max (0, heightHint - height);
 	/*
 	* Bug in GTK.  gdk_window_get_frame_extents() fails for various window
 	* managers, causing a large incorrect value to be returned as the trim.
@@ -2936,6 +2961,8 @@ public void setVisible (boolean visible) {
 			GTK.gtk_widget_show (shellHandle);
 			GTK3.gtk_window_resize(shellHandle, init_width[0], init_height[0]);
 			resizeBounds (init_width[0], init_height[0], false);
+			oldWidth = init_width[0];
+			oldHeight = init_height[0];
 		} else {
 			GTK.gtk_widget_show (shellHandle);
 		}
@@ -2975,7 +3002,7 @@ public void setVisible (boolean visible) {
 			if (!iconic) {
 				update (true, true);
 				if (isDisposed ()) return;
-				adjustTrim ();
+				adjustTrim (oldWidth, oldHeight);
 			}
 		}
 		mapped = true;

tests/org.eclipse.swt.tests.gtk/ManualTests/org/eclipse/swt/tests/gtk/snippets/Issue1161_InitialWrongShellSizeDialogTrim.java

@@ -0,0 +1,57 @@
+package org.eclipse.swt.tests.gtk.snippets;
+
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.graphics.Point;
+import org.eclipse.swt.layout.GridData;
+import org.eclipse.swt.layout.GridLayout;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Label;
+import org.eclipse.swt.widgets.Shell;
+
+/**
+ * Please remove $HOME/swt/trims.prefs to see the issue.
+ */
+public class Issue1161_InitialWrongShellSizeDialogTrim {
+	static String message = "Soooooooooooooooooooooooooooooooooooooooooooooooooome Extraaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.\n"
+			+ "Loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong Teeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeext";
+	/**
+	 * This problem happens with SWT.DIALOG_TRIM. In general any trim with No Resize
+	 * style
+	 */
+	static int style = SWT.DIALOG_TRIM;
+
+	public static void main(String[] args) {
+		Display display = new Display();
+		Shell shell = new Shell(display, style);
+		shell.setText("Issue1161_InitialWrongShellSizeDialogTrim");
+
+		// Even with the FillLayout issue exists.
+		GridLayout layout = new GridLayout();
+		layout.verticalSpacing = 20;
+		layout.marginBottom = layout.marginTop = layout.marginLeft = layout.marginRight = 10;
+		shell.setLayout(layout);
+
+		// many labels to make the dialog bigger
+		for (int i = 0; i < 8; i++) {
+			Label label = new Label(shell, SWT.NONE);
+			label.setText("Line:" + i + "  " + message);
+			label.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
+		}
+
+		Point size = shell.computeSize(SWT.DEFAULT, SWT.DEFAULT, true);
+		// x and y location are randomly chosen.
+		// width and height are correctly calculated.
+		shell.setBounds(600, 600, size.x, size.y);
+
+		shell.pack();
+		shell.open();
+
+		while (!shell.isDisposed()) {
+			if (!display.readAndDispatch()) {
+				display.sleep();
+			}
+		}
+		display.dispose();
+	}
+
+}