Develop Reference

Scrolling cause flickering when controlling MouseWheel events

I'm trying to understand what is executing before the MouseWheel event.
What I've done:
I have a form which has AutoScroll property set to true. There is a control (ZEDGRAPH) at the top and the bottom of this form.
To overcome the issue of scrolling and zooming at the same time I captured the mousewheel += new MouseEvenHandler(mymethod) for the form.Then using a bool variable I keep track of when the control (ZEDGRAPH) has focus and when it does not.
When it has focus I make verticalscroll.value = (int)mydesiredposition;
This works in accomplishing what I wanted which is to ignore the mousewheel event in the form and focus on the control.
What I am struggling with is the fact that when I scroll the form flickers every time and scrolls down before coming to the set scrollbar value.
So what I am wondering is what is getting triggered before this mouseeventhandler that causes it to flicker and is there a relatively simple workaround this?
My code snapshot:
public Form(Form1 f)
{
InitializeComponent();
this.MouseWheel += new MouseEventHandler(mousewheel);
}//end of constructor
//
//
bool mousehoverZedGraph1 = false;
bool mousehoverZedGraph2 = false;
//
//
private void zedGraphControl1_MouseHover(object sender, EventArgs e)
{
mousehoverZedGraph1 = true;
return;
}
private void mousewheel(object sender, MouseEventArgs e)
{
if (mousehoverZedGraph1 == true)
{
VerticalScroll.Enabled = false;
VerticalScroll.Value = 0;
return;
}
else if (mousehoverZedGraph2 == true)
{
VerticalScroll.Value = 429;
VerticalScroll.Enabled = false;
}
else
{
//VerticalScroll.Value += e.Delta;
}
}
private void Form_MouseEnter(object sender, EventArgs e)
{
mousehoverZedGraph1 = mousehoverZedGraph2 = false;
VerticalScroll.Enabled = true;
}
A small video highlighting the flicker:

Zooming in ComboBox not working as expected

I have an application that scans an image to display on the application. After the image is scanned, I have the option to zoom the image. There's a combo box on the application that display the zoom percentage as well.
I can zoom fine using my mouse wheel and the combo box % changes accordingly which is fine. The problem happens if I manually select the combo box and select a zoom percentage, say 50%, then there's no changes at all.
Code:
private void ImageBox_ZoomLevelsChanged(object sender, EventArgs e)
{
this.FillZoomLevels();
}
private void ZoomComboBox_Click(object sender, EventArgs e)
{
}
private void FillZoomLevels()
{
ZoomComboBox.Items.Clear();
foreach (int zoom in ImageBox.ZoomLevels)
ZoomComboBox.Items.Add(string.Format("{0}%", zoom));
}
Am I doing anything wrong? Appreciate any help.

When there is more than one control on the Panel, and the ScrollBars are shown, the MouseWheel event of the Panel would be raised, but if there's only a PictureBox on the Panel whose Image large enough to make the panel's ScrollBars visible, then the MouseWheel event of the Panel won't be raised, instead, the Form's MouseWheel event fires.
In the following sample, I just add a PictureBox onto the Panel without any other controls added, set a large Image to the PictureBox which make the Panel's ScrollBars invisible, since there's only one control on the panel, the MouseWheel event of the Panel won't be raised, but the Form's MouseWheel event be raised, we handle this event instead, handle the Form's KeyDown and KeyUp events as well.
Furthermore, set the SizeMode of the PictureBox to StretchImage instead of AutoSize, thus when we change the size of the PictureBox, the Image in the PictureBox will resize to fit the PictureBox.
The PictureBox.Scale() method won't help you in this screnario, change the size of the PictureBox instead.
public partial class Form4 : Form
{
public Form4()
{
InitializeComponent();
}
bool ctrlKeyDown;
bool shiftKeyDown;
private void Form4_Load(object sender, EventArgs e)
{
this.ctrlKeyDown = false;
this.shiftKeyDown = false;
//If there's only PictureBox control on the panel, the MouseWheel event of the form raised
//instead of the MouseWheel event of the Panel.
this.MouseWheel += new MouseEventHandler(Form4_MouseWheel);
this.KeyDown += new KeyEventHandler(Form4_KeyDown);
this.KeyUp += new KeyEventHandler(Form4_KeyUp);
//this is important for zooming the image
this.pictureBox2.SizeMode = PictureBoxSizeMode.StretchImage;
}
void Form4_KeyUp(object sender, KeyEventArgs e)
{
this.ctrlKeyDown = e.Control;
this.shiftKeyDown = e.Shift;
}
void Form4_KeyDown(object sender, KeyEventArgs e)
{
this.ctrlKeyDown = e.Control;
this.shiftKeyDown = e.Shift;
}
void Form4_MouseWheel(object sender, MouseEventArgs e)
{
bool IsGoUp = e.Delta > 0 ? true : false;
if (this.ctrlKeyDown)
{
if (IsGoUp && this.panel1.HorizontalScroll.Value > 5)
{
this.panel1.HorizontalScroll.Value -= 5;
}
if (!IsGoUp && this.panel1.HorizontalScroll.Value < this.panel1.HorizontalScroll.Maximum - 5)
{
this.panel1.HorizontalScroll.Value += 5;
}
}
else if (this.shiftKeyDown)
{
int hStep = (int)(this.pictureBox2.Image.Width * 0.02);
int vStep = (int)(this.pictureBox2.Image.Height * 0.02);
if (IsGoUp)
{
this.pictureBox2.Width += hStep;
this.pictureBox2.Height += vStep;
}
else
{
this.pictureBox2.Width -= hStep;
this.pictureBox2.Height -= vStep;
}
}
else
{
if (IsGoUp && this.panel1.VerticalScroll.Value > 5)
{
this.panel1.VerticalScroll.Value -= 5;
}
if (!IsGoUp && this.panel1.VerticalScroll.Value < this.panel1.VerticalScroll.Maximum - 5)
{
this.panel1.VerticalScroll.Value += 5;
}
}
}
}

WPF ComboBox: click outside of popup suppress mouse click

I use a standard WPF ComboBox control. When popup is opened and user clicks somewhere outside, popup is closed. But if there is button on the window and user clicks on it (with popup still opened), button's click handler is not executed. Popup is closed, but user has to click one more time on the button to raise click event on it.
I know that is standard behavior for this control. Have you any ideas how to bypass this behavior? Thanks!

I fixed some bugs with #Eng. M.Hamdy very good approach and did it in C#, also applying it to all comboboxes application wide.
Application hook:
EventManager.RegisterClassHandler(typeof(ComboBox), UIElement.PreviewMouseLeftButtonDownEvent, new MouseButtonEventHandler(FixComboBoxOutClick));
Handler code:
private void FixComboBoxOutClick(object sender, MouseButtonEventArgs e) {
if (sender is ComboBox combo) {
Point comboRelativePoint = Mouse.GetPosition(combo);
if (comboRelativePoint.X < 0 || comboRelativePoint.Y < 0 || comboRelativePoint.X > combo.ActualWidth || comboRelativePoint.Y > combo.ActualHeight) {
UIElement popupContent = combo.FindChild<Popup>(null).Child;
Point popupRelativePoint = Mouse.GetPosition(popupContent);
if (popupRelativePoint.X < 0 || popupRelativePoint.Y < 0 || popupRelativePoint.X > popupContent.RenderSize.Width || popupRelativePoint.Y > popupContent.RenderSize.Height) {
combo.IsDropDownOpen = false;
}
}
}
}
You can look for FindChild<T>() implementations here.

You can create an event for ComboBox DropDownClosed and with the hittestfunction, find the other control that the user has clicked.
private void ComboBox_DropDownClosed(object sender, EventArgs e)
{
Point m = Mouse.GetPosition(this);
VisualTreeHelper.HitTest(this, this.FilterCallback, this.ResultCallback, new PointHitTestParameters(m));
}
private HitTestFilterBehavior FilterCallback(DependencyObject o)
{
var c = o as Control;
if ((c != null) && !(o is MainWindow))
{
if (c.Focusable)
{
if (c is ComboBox)
{
(c as ComboBox).IsDropDownOpen = true;
}
else
{
var mouseDevice = Mouse.PrimaryDevice;
var mouseButtonEventArgs = new MouseButtonEventArgs(mouseDevice, 0, MouseButton.Left)
{
RoutedEvent = Mouse.MouseDownEvent,
Source = c
};
c.RaiseEvent(mouseButtonEventArgs);
}
return HitTestFilterBehavior.Stop;
}
}
return HitTestFilterBehavior.Continue;
}
private HitTestResultBehavior ResultCallback(HitTestResult r)
{
return HitTestResultBehavior.Continue;
}
Then in the FilterCallback function after finding that control, raise the mouse down event on that control.
I found the raise event, does not work on comboboxes so for clicking that, I simply set the IsDropDownOpen to true.
I found the code in here and modified it a little.

I used an easy solution:
In the PreviewMouseLeftButtonDown event, if the mouse pos is outside the combobox, close the dropdown. This will allow other control to get the mouse click:
Dim p = Mouse.GetPosition(combo)
If p.X < 0 OrElse p.Y < 0 OrElse p.X > combo.Width OrElse p.Y > combo.Height Then
cmb.IsDropDownOpen = False
End If

You can try to release the mouse capture right after the ComboBox gets one:
In your's ComboBox properties in XAML:
GotMouseCapture="ComboBox_OnGotMouseCapture"
And in code-behind:
private void ComboBox_OnGotMouseCapture(object sender, MouseEventArgs e)
{
ComboBox.ReleaseMouseCapture();
}

detect tabpage which is not selected but clicked C# windows form application

I am trying to build a web browser in Windows form application.I added an option of closing the tab in the contextmenu. I don't want the tabpage to be selected on right click, just the context menu needs to appear. That works fine. The problem is when I click close tab the previous tab is closed and not the current one as previous tab is the one which was selected. I tried to figure this out by getting the rectangle location of the tabpage but that appears to be the same for all the tabs. Please help!
//this is my event handler for closing the tab
private void closeToolStripMenuItem_Click(object sender, EventArgs e)
{
this.tabControlBrowser.TabPages.Remove(this.tabControlBrowser.SelectedTab);
}

Yest you are correct that is because you are using
this.tabControlBrowser.TabPages.Remove(this.tabControlBrowser.SelectedTab);
this will remove the current selected tab but not the tab page that you are clicking on.
Please try below code hope it will help you to move forward
TabPage _ClickedTab;
public Form1()
{
InitializeComponent();
this.tabControl1.MouseClick += new MouseEventHandler(tabControl1_MouseClick);
}
void tabControl1_MouseClick(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Right)
{
this.contextMenuStrip1.Show(this.tabControl1, e.Location);
Rectangle r2 = this.tabControl1.GetTabRect(0);
foreach (TabPage item in this.tabControl1.TabPages)
{
Rectangle r = this.tabControl1.GetTabRect(tabControl1.TabPages.IndexOf(item));
if (r.X < e.Location.X && e.Location.X < r.X + r.Width && r.Y < e.Location.Y && e.Location.Y < r.Y + r.Height)
{
_ClickedTab = item;
}
}
}
}
private void toolStripMenuItem3_Click(object sender, EventArgs e)
{
this.tabControl1.TabPages.Remove(_ClickedTab);
}

You could test the location of the mouse against the rectangles returned by TabControl#GetTabRect

Moving a control within another control's visible area

I have a PictureBox that is inside a TabPage, and of course this TabPage is part of a TabView and this TabView is inside a Form. I want users be able to move this picture box within the tab page. For this I am using the MouseDown, MouseMove and MouseUp events of the picture box:
private void pictureBoxPackageView_MouseDown(object sender, MouseEventArgs e)
{
if (!_mapPackageIsMoving)
{
_mapPackageIsMoving = true;
}
}
private void pictureBoxPackageView_MouseMove(object sender, MouseEventArgs e)
{
if(_mapPackageIsMoving)
{
pictureBoxPackageView.Location = MousePosition; //This is not exact at all!
return;
}
//Some other code for some other stuff when picturebox is not moving...
}
private void pictureBoxPackageView_MouseUp(object sender, MouseEventArgs e)
{
if (_mapPackageIsMoving)
{
_mapPackageIsMoving = false; //Mouse button is up, end moving!
return;
}
}
But my problem lies in the MouseMove event. As soon as I move mouse after button down, the picture box jumps out of tab page's visible area.
I need to know how to handle the move only within the rectangle of the tab page, and if picture box is being dragged out of tab view's visible area, it shouldn't move anymore unless user brings the mouse inside the tab view's visible rectangle.
Any helps/tips will be appriciated!

You need a variable to hold the original position of the PictureBox:
Modified from a HansPassant answer:
private Point start = Point.Empty;
void pictureBoxPackageView_MouseUp(object sender, MouseEventArgs e) {
_mapPackageIsMoving = false;
}
void pictureBoxPackageView_MouseMove(object sender, MouseEventArgs e) {
if (_mapPackageIsMoving) {
pictureBoxPackageView.Location = new Point(
pictureBoxPackageView.Left + (e.X - start.X),
pictureBoxPackageView.Top + (e.Y - start.Y));
}
}
void pictureBoxPackageView_MouseDown(object sender, MouseEventArgs e) {
start = e.Location;
_mapPackageIsMoving = true;
}