Develop Reference

C# WPF - MouseLeftUp Event doesn't appear to fire [duplicate]

On System.Windows.UIElement there is a CaptureMouse() and a paired ReleaseMouseCapture() method. In this WPF DragDrop sample they call CaptureMouse on MouseDown and release it on MouseUp. The documentation in MSDN is about as useless as it comes - "CaptureMouse -> Captures the mouse."
In my head before trying it I assumed that it somehow locked the mouse inside the UIElement bounds, but that's clearly not the case when I try it. From experimenting, it seems to have something to do with responding to events when the mouse is outside of the UIElement, but not wanting to be a cargo cult programmer I don't want to just use it because the example does, I'd like an authoritative description of what it means.

From Capture and Uncapture the Mouse on MSDN:
When an object captures the mouse, all mouse related events are treated as if the object with mouse capture perform the event, even if the mouse pointer is over another object.
Only the capturing control receives the mouse events until released.
Capturing the mouse is useful for dragging because all the dragging code can exist in the one control, rather than being spread over multiple controls.

When it has captured the mouse, a control will receive mouse events even if the mouse pointer is no longer within its bounding area.
Typically, it's used for:
Drag and drop
Buttons (to handle Mouse Up when you put the mouse down on the button and move the mouse before you release the button)

The Silverlight 2 documentation for it has a more verbose description, I don't know why it isn't a part of the 3.5 documentation page too:
When an object has captured the mouse, that object receives mouse input whether or not the mouse pointer is within its bounding area. The mouse is typically only captured during simulated drag operations.
...
It works the same with WPF, and so the reason it is used with DragDrop, is that is how the
it knows to report back to the control being dragged from when the mouse may be outside of that control. If you comment out the MyCanvas.Capture() and the Capture(Null) (which clears it) then you can no longer drop.

Unity Button not working/highlighting/interacting

I have made the program so that, once the level is done, a panel will pop up and this button is attached. However this button is not working.
I have - Checked my eventsystem, Checked Raycast Settings, Set the onclick event, Also brought the button out on the z axis so that it would have no interference from the panel.
My Hierarchy
Button's Inspector
Canvas' Inspector

It's because you original color of the Image is completely black. The Button component just tries to tint the original color, but because it's black, you see no effect.
Oh, and... As #Glurth said, you have enabled Block Raycast on the CanvasGroup, so basiclly the Button doesn't even receive pointer events.

I see you have "Blocks Raycasts" configured for the Canvas group, which you have added to the canvas itself.
I don't think this component is supposed to go on the canvas itself anyway; it's intended to allow one to disable or hide groups of objects on your canvas. The "blocks raycasts" is intended to prevent clicking on controls that are behind this group, and collect clicks for the group itself. If you put everything on your canavas in this group, it will collect all the clicks for everything.

I found my problem, i had 'ignore parent groups' unchecked which did not allow the mouse pointer to recognise the button as it was a 'child' of canvas
Thankyou all for your help!
My Canvas Inspector component, Canvas Group

IsResizing or equivalent in C#

I'm looking for a way to check during a resizing event whether the control is currently being resized or whether it has reached its final size. (C# Windows Forms)
E.g. In Java with sliders, you can tell whether the user is currently sliding or whether they have released the mouse - this means that you can avoid expensive redraws or other calculations until the final value has been chosen.
Thanks in advance for any info.

The Form has a few events to help you with this
There's the ResizeBegin, Resize, and ResizeEnd Events. A combination of them should get you what you want.
Further notes:
When you click and drag the border of a window, the event sequence is ResizeBegin, repeated Resize for each move of the mouse, ResizeEnd. When you minimize, maximize or restore the window size, then Resize is called once for each of those. A ResizeBegin and ResizeEnd pair is also called for simply moving the window around as well by the title bar, though not when you programatically set the windows Location property.

In WPF, how can I capture mouse on a Canvas and still find what controls the cursor is hovering over?

I have a custom Canvas control (inherited from Canvas) overlaid over a large area of User Controls. The idea is to draw paths between user controls (i.e. connector lines).
To capture mouse movement, I call Mouse.Capture(theCanvas) on MouseDown. This works beautifully, but the user controls under the canvas obviously no longer receive mouse events. Mouse.DirectlyOver always shows the canvas, so I can't really fake it by peeking at the current position and seeing which user control it's over.
So, I still need the Canvas for drawing paths, but how can I solve this one of the following ways:
Peek under the Canvas and see what the topmost control is right under it?
Get this MouseDown -> Track MouseMoves -> MouseUp workflow to work on the canvas without mouse captures?
Any other ideas welcome...

I'd agree that those are your two options. If you want to only forward some clicks to your usercontrols, then go with option 1, and hit test the controls under the canvas.
If you need your usercontrols to behave as though there is nothing covering them (textboxes, buttons etc), then i'd recommend using the PreviewMouseMove event on the user control's parent, as this can pick up and optionally "handle" events before the controls get at the event, but it won't block the event if you don't set handled to true

Mouse movement capture

I have an application wich open a modal form with the ShowDialog method.
Once this form is displayed I want to capture the mouse movement even if the cursor is outside the form.
How can I capture the mouse movement? I saw something with the Capture property but I cannot manage to make it work.
[edit]
I want to be notified if the mouse move outside the form.

The Capture property is the correct way, but there are some limitations.
Only the foreground window can capture the mouse
Mouse capturing can be disabled by other parts of the system
The Win32 API function SetCapture gets reset everytime a "mouse up" event occours. I assume that also applies for .NET.
See the remarks section of Capture property.
When the mouse is captured, you'll receive the usual events but with a wider mouse coordinate range (for example a negative X position, if the mouse is left of the capturing control)
Mouse capturing is fragile, because of it's global nature. Check if there are other ways to handle certain events. Perhaps the MouseLeave or MouseEnter events are enough in your case.

You can just use the static property Control.MousePosition.

You can read the position of the cursor, using the Cursor.Position property, see Cursor.Position