When a form loads, I'd like it to show a loading image (within a Picture Box) and a standard Windows label with some text. However, all I see are white boxes, or sometimes I see another form underneath. How do I get the image and label to display properly.
I've tried setting AllowTransparency to false when the form loads, and also setting the Transparency Key of the form to some other colour, but nothing has worked.
The project is C# .Net v3.5 (also tried v4 and v4.5).
Any ideas?
First, you can't display an image, busy-wait, and then change the image - this will never redraw anything, leading to the symptoms you describe. To "wait" you will need to return control to your main application loop so it can continue to process messages (e.g. to handle redraw requests for your window). One way to do what you want is to display your initial state (splash screen) and then use a timer to call you back later to change the display to your second state.
The next problem you face is using forms controls with transparency. Most controls treat "transparent" as "fill your background with your parent controls color", which is not what you want. An easy way around this is to implement a Paint handler and draw the image and text for yourself - this gives you much more control of how your display looks, and will also allow you to get a cleaner redraw (no flicker or other problems caused by the display being built up but by bit in several controls)
Lastly, consider implementing your splash screen display as a separate control/form that you show above your main form during loading, as that makes it easy to "overlay" on your main form without having to change its design at all.
Just write formObjectName.Refresh() after formObjectName.Show()
Related
How to prevent premature painting of MemoEdit control when the form is loading?
I have a form which is DevExpress.XtraBars.Docking.ControlContainer.
Red area in the pic.1 is the devexpress LayoutControl which consists of a bunch of LayoutControlItems, almost all of them have a TextEdit editors, but the second one from top is MemoEdit.
In the pic.2 is the what i see when the form is loading (after i called Show()).
As you can see, other controls are not drawn or displayed at the moment, but the MemoEdit do. I tried to use LockWindowUpdate, Begin/End Update, SuspendLayout but isn't working.
I would like to know what are reasons of this behaviour.
I want to specify something. Even when form is loaded and the LayoutControl was once filled with controls, MemoEdit still doing strange things, for example when I am switch between horizontal tabs (pic. 3 and pic. 4). At the moment when I select tab, that was already once "loaded" MemoEdit starts painting at old tab.
I'm trying to place a transparent and borderless child (WinForm) form on top of another child (WinForm) form that is opaque, but I'd like to retain the ability to directly click on the transparent form. There are a few answers on the web regarding making a transparent form that can be clicked through, but I want to make one that I can click on.
I've found this answer, which shows that setting my transparent form's BackColor and TransparencyKey to something specific like Color.Red achieves the desired behavior. However based on this answer, it seems this behavior between certain Colors and TransparencyKey may actually be a long-running bug.
Ideally I don't want to rely on a bug to achieve a desired effect. What would be a more "appropriate" approach for making a clickable, transparent, and borderless (WinForm) form?
Update (Additional Context):
I'm basically creating a screen pixel previewer for color data extraction.
Overlay forms containing captured bitmap(s) of the screen area.
Another form that gives a visual indicator for the pixel area being previewed (small black box in the below snapshot). This form is placed above the bitmap forms. I have this form as transparent (to see through to the below bitmaps), but I still want to be able to click on it for event processing.
Without the TransparencyKey = BackColor = Color.Red trick, clicking within the small black box causes focus to move to the below bitmap form, which then covers up the small box form and the preview window showing the zoomed view. The purpose of the click is to capture the cursor position for additional processing. I can work around this by immediately giving focus back to the small box + preview forms, but that occasionally causes flicker.
I have a winforms C# application that opens multiple dialog boxes. To suit the style of the application, I have removed the default title bars for each window and created my own (with control buttons and drag-to-move function).
The problem that now faces me is that without a titlebar, the user has no way of telling which window is the 'active' window when they are manually moved apart (so they are not overlapping).
In any windows application (that uses titlebars), when you try to navigate away from a dialog box back to the main program (without closing the dialog box) - it wont let you. The border of the dialog box flashes and you hear a windows error sound. Some kind of equivalent visual feedback would be great without needing to have the default titlebars - and tinting an entire window darker seems like it would do the trick nicely.
Something like this in pseudo-code, which would nicely tint the parent window whilst a dialog is open:
// tint window now
window.ShowDialog();
// un-tint window
I have tried to place a panel covering everything with colour set to 'transparent' (with the intention of later controlling the opacity of the panel) but the transparency does not seem to work. Any other ideas of accomplishing this? Or does anyone have a better suggestion to achieve the same level of visual feedback?
Summary:
Is there any way to tint an entire window, or overlay it with a colour? If not, could anyone suggest an alternate method of making the window appear 'inactive'?
I would suggest you to create a method in forms you want to disable:
void DisableForm()
{
//some fancy color
this.BackColor = System.Drawing.Color.Khaki;
//and disable all controls owned by form, just to be sure
foreach (var s in this.Controls)
{
((Control)s).Enabled = false;
}
}
and functions which enables back those forms of course.
edit.
also you can set visibility property of controls to false
I have a Windows Forms control (a subclass of Panel) that serves as a panel that displays an image. The background of the control serves as the image that is displayed to the user.
The image itself is generally a screenshot of whatever is behind the application. The method of obtaining this screenshot is to hide the application and have the user press a button.
When that button is pressed, the screenshot is saved as the background of the Windows Forms control, and then the application is shown again. The background doesn't appear to update
until the control is visible again, and this causes a noticeable flicker of sorts as the old background switches to the new background. Is there a way to cause the background to
change while the control is hidden and remove this flicker?
Code:
public void updateBackground()
{
Image bg = null;
do
{
// this just gets the background using gdi32 and user32 calls
bg = Utilities.getDesktopImage();
}
while (bg == null);
// this function invokes the GUI thread to change the BackgroundImage of the
// drawPanel
drawPanel.setBackground(bg)
// drawPanel is a child control to the main Form
mainForm.show();
}
I have also tried using various forms of Refresh() and Invalidate() to get the control to update before it is shown. Application.DoEvents() seems to improve the speed, but there is still a noticible change from the old background to the new one.
Is there something that I'm missing? I can't seem to find what I'm looking for on Google, or elsewhere on StackOverflow.
Thanks.
Try moving your logic to another thread (Task, Backgroundworker or ThreadPool). This shall remove the lag you see.
The flicker occurs because (I assume) you do some relatively lengthy work in the UI thread, which blocks graphic message loop and everything "freeze" for a fraction of a second.
Are you using Win7 or Vista and is the Desktop Window Manager Service running?
Does the problem go away when the DWM is disabled (Control Panel --> Administrative Tools --> Services --> Desktop Window Manager Session Manager)?
It sounds like an issue with Aero - the way the DWM works is that the form's graphics buffer is not updated while it is hidden. The DWM stores the data from the last visible paint and doesn't refresh until the form is visible again. This causes the previous form canvas to be visible briefly until Windows gets around to repainting the changes since it was last visible (ie: the flicker).
This article discusses some of the topics :
http://blogs.msdn.com/b/greg_schechter/archive/2006/05/02/588934.aspx
There is probably a way to override some of this behaviour but I'm not familiar with it off the top of my head. Tagging this with GDI+ may help get better answers.
We have a mapping form in our application that needs a Google Earth background image, and as you can't use the Google Earth plugin in a browser that is under a panel, we use a second form to show the background image. We have a transparent panel on the mapping form that the drawing is done on while Google Earth is drawn on a form held in sync below.
We achieve transparency by giving the form a transparency key of 255, 250, 250 and setting the panel background to this color before drawing on it. Although now after looking at the information available online it appears that the panel shouldn't ever get cursor events.
This works perfectly in most cases, but on one or two customers machines (one is definatly Windows 7) the cursor will not work correctly on the panel where it is transparent. If the cursor is placed over a drawn area of the map then it all work fine.
I think the issue is due to transparancy click through but as it works in most cases I'm not sure what is exactly going on. We've updated all of the graphics drivers to see if there is a custom setting on the customers machine but this hasn't helped.
Does someone have a definative description of what the transparency key does? Is there a way to absolutly set that the panel should recieve the mouse events?
EDIT
Added detail about transparency key.
Try intercepting the WM_HITTEST message in the WndProc for the Form window and when you know it is over the client area return the appropriate HTCLIENT value. It could be that the default window processing is sometimes returning a different value.
Stevo - Have you ever figured out an answer to this? I had the same problem and figured out to change the transparency key of the main form to some odd color. May or may not help you. I had a custom control with transparency but the forms key color was also my drawing color, thus allowing it to click through (strangely). I changed it and it worked!