greenshot/GreenshotPlugin/Controls/ThumbnailForm.cs

/*
 * Greenshot - a free and open source screenshot tool
 * Copyright (C) 2007-2021 Thomas Braun, Jens Klingen, Robin Krom
 * 
 * For more information see: http://getgreenshot.org/
 * The Greenshot project is hosted on GitHub https://github.com/greenshot/greenshot
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 1 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
using System;
using System.Windows.Forms;
using GreenshotPlugin.Core;
using System.Drawing;
using GreenshotPlugin.Core.Enums;
using GreenshotPlugin.IniFile;
using GreenshotPlugin.UnmanagedHelpers;
using GreenshotPlugin.UnmanagedHelpers.Enums;
using GreenshotPlugin.UnmanagedHelpers.Structs;

namespace GreenshotPlugin.Controls {
	/// <summary>
	/// This form allows us to show a Thumbnail preview of a window near the context menu when selecting a window to capture.
	/// Didn't make it completely "generic" yet, but at least most logic is in here so we don't have it in the mainform.
	/// </summary>
	public sealed class ThumbnailForm : FormWithoutActivation {
		private static readonly CoreConfiguration conf = IniConfig.GetIniSection<CoreConfiguration>();

		private IntPtr _thumbnailHandle = IntPtr.Zero;

		public ThumbnailForm() {
			ShowInTaskbar = false;
			FormBorderStyle = FormBorderStyle.None;
			TopMost = false;
			Enabled = false;
			if (conf.WindowCaptureMode == WindowCaptureMode.Auto || conf.WindowCaptureMode == WindowCaptureMode.Aero) {
				BackColor = Color.FromArgb(255, conf.DWMBackgroundColor.R, conf.DWMBackgroundColor.G, conf.DWMBackgroundColor.B);
			} else {
				BackColor = Color.White;
			}

			// cleanup at close
			FormClosing += delegate {
				UnregisterThumbnail();
			};
		}

		public new void Hide() {
			UnregisterThumbnail();
			base.Hide();
		}

		private void UnregisterThumbnail()
        {
            if (_thumbnailHandle == IntPtr.Zero) return;

            DWM.DwmUnregisterThumbnail(_thumbnailHandle);
            _thumbnailHandle = IntPtr.Zero;
        }

		/// <summary>
		/// Show the thumbnail of the supplied window above (or under) the parent Control
		/// </summary>
		/// <param name="window">WindowDetails</param>
		/// <param name="parentControl">Control</param>
		public void ShowThumbnail(WindowDetails window, Control parentControl) {
			UnregisterThumbnail();

			DWM.DwmRegisterThumbnail(Handle, window.Handle, out _thumbnailHandle);
            if (_thumbnailHandle == IntPtr.Zero) return;

            var result = DWM.DwmQueryThumbnailSourceSize(_thumbnailHandle, out var sourceSize);
            if (result.Failed())
            {
                DWM.DwmUnregisterThumbnail(_thumbnailHandle);
                return;
            }

            if (sourceSize.IsEmpty)
            {
                DWM.DwmUnregisterThumbnail(_thumbnailHandle);
                return;
            }

            int thumbnailHeight = 200;
            int thumbnailWidth = (int)(thumbnailHeight * (sourceSize.Width / (float)sourceSize.Height));
            if (parentControl != null && thumbnailWidth > parentControl.Width)
            {
                thumbnailWidth = parentControl.Width;
                thumbnailHeight = (int)(thumbnailWidth * (sourceSize.Height / (float)sourceSize.Width));
            }
            Width = thumbnailWidth;
            Height = thumbnailHeight;
            // Prepare the displaying of the Thumbnail
            var dwmThumbnailProperties = new DWM_THUMBNAIL_PROPERTIES
            {
                Opacity = 255,
                Visible = true,
                SourceClientAreaOnly = false,
                Destination = new RECT(0, 0, thumbnailWidth, thumbnailHeight)
            };
            result = DWM.DwmUpdateThumbnailProperties(_thumbnailHandle, ref dwmThumbnailProperties);
            if (result.Failed())
            {
                DWM.DwmUnregisterThumbnail(_thumbnailHandle);
                return;
            }

            if (parentControl != null) {
                AlignToControl(parentControl);
            }

            if (!Visible) {
                Show();
            }
            // Make sure it's on "top"!
            if (parentControl != null) {
                User32.SetWindowPos(Handle, parentControl.Handle, 0, 0, 0, 0, WindowPos.SWP_NOMOVE | WindowPos.SWP_NOSIZE | WindowPos.SWP_NOACTIVATE);
            }
        }

		public void AlignToControl(Control alignTo) {
			var screenBounds = WindowCapture.GetScreenBounds();
			if (screenBounds.Contains(alignTo.Left, alignTo.Top - Height)) {
				Location = new Point(alignTo.Left + (alignTo.Width / 2) - (Width / 2), alignTo.Top - Height);
			} else {
				Location = new Point(alignTo.Left + (alignTo.Width / 2) - (Width / 2), alignTo.Bottom);
			}
		}
	}
}