I have written some code to change a button's background image on mouse-hover, however when the image is changes it seems that it is a bit slow to complete.
That is, the process of setting the new picture as its background image is slow. By slow I mean a few milliseconds, but still enough to be seen!
Is there anything I can do about this, to speed up this process?
let use mouse move (the mouse overed control)
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So I'm pulling some stuff from a database via a different thread, and want the form to remain usable while doing so, and also want to show the user a progress indicator until the DB code finishes.
In 'normal' winforms I'd use a ProgressBar with the ProgressBarStyle set to Continuous, but CF doesn't have that. Neither does it seem to support animated GIFs in a PictureBox (which would have been an easy way).
So what are my options for doing something like this?
EDIT: Don't want to use an hourglass mouse cursor because that implies to the user that the UI is busy (it's not).
Thanks
You could look for a 3rd party progress bar control that supports the Continuous progress bar style, or a control that supports animated gifs - you're not the first running into this limitation, but I'm not sure if there are any good ones out there.
Rolling your own "continuous" progress bar UserControl shouldn't be very hard, you get a decent result with just a timer to call Invalidate, and using Graphics.FillRectangle in the Paint event.
An alternative to an animated gif control could be to create a "film strip" UserControl, where you provide an image (non-gif) that contains all "frames" of the gif layed out horizontally or vertically. Again you'd need a timer to call Invalidate and increase the frame number, and Graphics.DrawImage has an overload to specify which portion of the film strip image is drawn.
Instead of the timer you could use #josef's comment to increment the "current frame" whenever the worker thread has finished a portion of the work. The animated gif's "movement" would then actually show the user that work is being done.
I have a picturebox with a fixed sized image (256x256) generated by the program. I have another smaller image as a resource. What I want to do is when my cursor is over the image and I hold down the mouse button, the smaller image "anchors" with the mouse pointer so it moves around with it. If I let go of the mouse button, the smaller image will stay in that position on top of the bigger image. The smaller image is basically a marker, something like an X or O.
I was thinking of having a second picturebox on top of the first picturebox but I can't make it transparent. Or redrawing the image with the smaller image on top of it and reloading the image into the picturebox, but I'm not sure how to do that and I think it's going to be pretty slow redrawing it each time I move the mouse.
So how can I have a marker image move around on top of a bigger image and have it stay there?
Create your control for this instead of using PictureBox. PictureBox should be used ONLY for fixed images on the form, nothing else.
Instead, derive your control from UserControl. Turn on double buffering for it. In OnPaint method, first draw your background picture, then your marker picture after it. Don't worry, it WON'T be slow and it WILL work as it should.
When you release the mouse, update background picture by drawing your marker picture on it.
Since every sentence here is a little discovery by itself, hope you'll have a good time coding your little game :)
I'm trying to create a undo functionality to a picture box by saving the image right before the paint take place into a array or something. I tried with List but i get the same image all the time, with Image List the size is to small for my porpoises. What are the best practices for saving undo data or how can i store images into memory right before every paint take place? Thank you !
You have to clone the image contents every time. I think you are adding always the reference of the image to the list.
If you want to get undo functionality done properly have a look at the Command Pattern.
Another way would be to calculate the difference of the original image and the image after the operation and then store the difference to save memory.
Many paints will take place on the same image. Windows fires the Paint event whenever part of the control needs to be repainted. Like when you drag another window across the PB. Or minimize and restore the form.
In other words, Paint doesn't tell you that the image changed. You'll need to derive your own class from PictureBox and override the Image property. The setter will be called when the image is changed.
How can I speed up the scrolling of UserControls in a WinForms app.?
My main form has trouble scrolling quickly on slow machines--painting for each of the small scroll increments is CPU intensive.
My form has roughly fifty UserControls (with multiple fields) positioned one below the other.
I’ve tried intercepting OnScroll and UserPaint in order to eliminate some of the unnecessary re-paints for very small scroll events, but the underlying Paint gets called anyway.
How can I streamline scrolling on slower machines?
The tried-and-true method is to use an offscreen bitmap which is updated only when the data represented by your control actually changes; then, all OnPaint needs to do is render that bitmap to the screen.
If your paint process is intensive, and since you have so many controls, you'll find this makes a massive difference to the performance of your application.
Note that using the DoubleBuffering control property won't help in your case--it does tell WinForms to render to an offscreen bitmap before rendering to the screen, but that still happens at every paint cycle since WinForms doesn't keep track of when the representation has changed.
So, you'd have to roll your own. It's not that difficult. Here's what looks like a reasonably good article on the subject.
You can also increase the size of the scroll step. For example
panel1.VerticalScroll.SmallChange = 100;
Will cause the panel to scroll it's content 100 units vertically per click of the scrollbar button. So you take bigger steps each time, that might make the experience feel better at least. And you can do the same for the horizontal scroll bar of course.
I have used tabs to eliminate scrolling.
I need to "animate" an arrow. It can go in any direction (up, down, left, right and diagonals) and the arrowhead will be at the end. It needs to appear as if it is growing from orgin to the end.
To make matters more complicated it has to be in a user control so it is possible to add to the controls collection in the forms and remove it to delete it from the screen, and its background is really transparent (no color.transparent) so i can't paint the background to "clear" the previous line.
I have it static already (drawn from origin to end) but i can't animate it. I tried to add a timer in the user control but I fail to get a correct algorithm to calculate the intermediate ends of the line while it is growing.
Any help would be appreciated.
Thanks
When using animation on a Windows form you have to use another thread. Look into using a background worker: http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker.aspx
You don't need another thread - I have succesfully implemented Windows Forms animation.
My design:
Use a Windows.System.Forms.Timer object to call a callback function 'Animate()' at regular intervals
the Animate() function updates a property of your arrow, and then calls Invalidate() on the windows control
this all happens in the same UI thread, so yuo will not get any flicker effects (as long as your control has double duffering switched on).