Develop Reference

How to prevent PictureBox internally refreshes itself?

I have a very fast loop which renders animation in a Bitmap buffer and adds filter to it (by using LockBits/UnlockBits to access to the raw data and Marshaling changes to it.) in an independent thread.
I wanted to figure out a way to display the render on the Form, real-time, so I created a PictureBox and linked its Image to the bitmap I created. Everytime immediately after the bitmap is unlocked, I refreshed the PictureBox (using delegate, to do cross-threading) so that the rendering is updated properly.
It's totally fine and works very fast, but one big problem came out as I tried dragging the form to the border of the screen, to see if any bug would appear, and oops, the app collapse..saying 'the bitmap is being locked' This happens when either there's other window moving above the PictureBox or the PictureBox is dragged partially out of the screen. I suspice it because PictureBox can refresh itself when redraw is neccessary, and it does when the bitmap is still being locked. So...any way to sovle this problem? Or anyother ways to render the my animation better?

One of possible solutions could be is create your custom MyPictureBox : PictureBox (say) class which override OnPaintBackground, like this:
protected override OnPaintBackground(...)
{
// nothing, an empty method
}
But I'm not very sure that this will work, you should to check this by yourself.
What I would do, personally, considering your comment:
I have a very fast loop which renders animation in a Bitmap buffer and
adds filter to it (by using LockBits/UnlockBits to access to the raw
data and Marshaling changes to it.) in an independent thread
just forget about PictureBox, cause I found it, personally, too generic and non suitable for high performance rendering. Just write a simple class that handles the drawing of specified bitmap on specified surface.
Imo, this is a best choice.

You can't do that.
Instead, you should copy the image (on the background thread) and put the copy in the PictureBox.
For better performance, you can swap between two images to avoid creating too many images.

How to effectively draw on desktop in C#?

I want to draw directly on the desktop in C#. From searching a bit, I ended up using a Graphics object from the Desktop HDC (null). Then, I painted normally using this Graphics object.
The problem is that my shapes get lost when any part of the screen is redrawn. I tried a While loop, but it actually ends up drawing as fast as the application can, which is not the update rate of the desktop.
Normally, I would need to put my drawing code in a "OnPaint" event, but such thing does not exist for the desktop.
How would I do it?
Example code: https://stackoverflow.com/questions/1536141/how-to-draw-directly-on-the-windows-desktop-c

I posted two solutions for a similar requirement here
Basically you have two options.
1- Get a graphics object for the desktop and start drawing to it. The problem is if you need to start clearing what you have previously drawn etc.
Point pt = Cursor.Position; // Get the mouse cursor in screen coordinates
using (Graphics g = Graphics.FromHwnd(IntPtr.Zero))
{
g.DrawEllipse(Pens.Black, pt.X - 10, pt.Y - 10, 20, 20);
}
2- The second option that I provide in the link above is to create a transparent top-most window and do all your drawing in that window. This basically provides a transparent overlay for the desktop which you can draw on. One possible downside to this, as I mention in the original answer, is that other windows which are also top-most and are created after your app starts will obscure your top most window. This can be solved if it is a problem though.
For option 2, making the form transparent is as simple as using a transparency key, this allows mouse clicks etc. to fall through to the underlying desktop.
BackColor = Color.LightGreen;
TransparencyKey = Color.LightGreen;

When you draw to HDC(NULL) you draw to the screen, in an unmanaged way. As you've discovered, as soon as windows refreshes that part of the screen, your changes are overwritten.
There are a couple of options, depending upon what you want to achieve:
create a borderless, possibly
non-rectangular window. (Use
SetWindowRgn to make a window
non-rectangular.) You can make this a child of the desktop window.
subclass the desktop window. This is not straightforward, and involves
injecting a DLL into the
Explorer.exe process.

To get an OnPaint for the desktop you would need to subclass the desktop window and use your drawing logic when it receives a WM_PAINT/WM_ERASEBKGND message.
As the thread you linked to says, you can only intercept messages sent to a window of an external process using a hook (SetWindowsHookEx from a DLL).
As mentioned a transparent window is another way to do it, or (depending on the update frequency) copying, drawing and setting a temporary wallpaper (as bginfo does).

This is difficult to do correctly.
It will be far easier, and more reliable, to make your own borderless form instead.

Smooth Text On Glass

I have seen many other samples out there that draw smooth text on glass. But I can't use them. I need every single label that gets added at runtime to be smooth. I can't just "draw" text onto the screen.
Is this at all possible, and are there and sources around?
Thank you

Take a long at this article http://msdn.microsoft.com/en-us/magazine/cc163435.aspx#S6
It's a bit long but it answers alot of your question and alore more in regards to glass.
but the relevant part for you directly is
One particular gotcha is that
rendering a GDI item in black uses the
bit pattern 0x00000000-which also
happens to be a completely transparent
black if you are using an alpha
channel. This means that if you draw
with a black GDI brush or pen you'll
get a transparent color, not a black
one. The biggest problem this presents
is when you try to use the default
text color in a control of a text
label that sits on the glass area.
Since the default text color is
usually black, the DWM will consider
this to be transparent and the text
will be written in the glass
incorrectly. An example can be seen in
Figure 10. The first line is written
with GDI+, the second is a text label
control using the default color. As
you can see, it's nearly illegible
because it's actually incorrectly
rendered text that shows up as gray,
not black.
Happily, there are a number of ways
around this problem. Using owner-draw
controls is one. Rendering to a bitmap
that has an alpha channel is another.
Fortunately, the easiest way to get
text on controls is to let the .NET
Framework 2.0 use GDI+ for you. This
is easily accomplished by setting the
UseCompatibleTextRendering property on
your controls. By default, this
property is set to false so that
controls written for previous versions
of the .NET Framework will render the
same. But if you set it to true, your
text will come out looking correct.
You can set the property globally with
the
Application.SetUseCompatibleTextRenderingDefault
method.
He also provides example code you can place in your Main()
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(true);
Application.Run(new GlassForm());
}
But I recommend reading the article, It'll clear up alot of what's going on with Aero/Glass
Cheers,
Phyx

Winforms: SuspendLayout/ResumeLayout is not enough?

I have a library of a few "custom controls". Essentially we have our own buttons, rounder corner panels, and a few groupboxes with some custom paint. Despite the "math" in the OnPaint methods, the controls are pretty standard. Most of the time, all we do is draw the rounded corners and add gradient to the background. We use GDI+ for all that.
These controls are ok (and very nice looking according to our customers), however and despite the DoubleBuffer, you can see some redrawing, especially when there are 20++ buttons (for example) on the same form. On form load you see the buttons drawing… which is annoying.
I'm pretty sure that our buttons are not the fastest thing on earth but my question is: if double buffer is "on", shouldn't all that redraw happen in background and the Windows subsystem should show the results "instantly" ?
On the other hand, if there's "complex" foreach loop that will create labels, add them to a panel (double buffered) and change their properties, if we suspendlayout of the panel before the loop and resume layout of the panel when the loop is over, shouldn't all these controls (labels and buttons) appear "almost instantly"? This doesn't happen like that, you can see the panel being filled.
Any idea why this is not happening? I know it's hard to evaluate without sample code but that's hard to replicate too. I could make a video with a camera, but trust me on this one, it's not fast :)

We've seen this problem too.
One way we've seen to "fix" it is to completely suspend drawing of the control until we're ready to go. To accomplish this, we send the WM_SETREDRAW message to the control:
// Note that WM_SetRedraw = 0XB
// Suspend drawing.
UnsafeSharedNativeMethods.SendMessage(handle, WindowMessages.WM_SETREDRAW, IntPtr.Zero, IntPtr.Zero);
...
// Resume drawing.
UnsafeSharedNativeMethods.SendMessage(handle, WindowMessages.WM_SETREDRAW, new IntPtr(1), IntPtr.Zero);

One of the things you should look at is whether you have set BackColor=Transparent on any of the child controls of your panels. The BackColor=Transparent will significantly degrade rendering performance especially if parent panels are using gradients.
Windows Forms does not use real transparency, rather it is uses "fake" one. Each child control paint call generates paint call on parent so parent can paint its background over which the child control paints its content so it appears transparent.
So if you have 50 child controls that will generate additional 50 paint calls on parent control for background painting. And since gradients are generally slower you will see performance degradation.
Hope this helps.

I'll approach your problem from a performance angle.
foreach loop that will create labels,
add them to a panel (double buffered)
and change their properties
If that's the order things are done, there's room for improvement. First create all your labels, change their properties, and when they are all ready, add them to the panel: Panel.Controls.AddRange(Control[])
Most of the time, all we do is draw
the rounded corners and add gradient
to the background
Are you doing the same thing over and over again? How are your gradients generated? Writing an image can't be that slow. I once had to create a 1680x1050 gradient in-memory, and it was really fast, like, too fast for Stopwatch, so drawing a gradient can't be so hard.
My advice would be to try and cache some stuff. Open Paint, draw your corners and save to disk, or generate an image in-memory just once. Then load (and resize) as needed. Same for the gradient.
Even if different buttons have different colors, but the same motif, you can create a bitmap with Paint or whatever and at runtime load it and multiply the Color values by another Color.
EDIT:
if we suspendlayout of the panel before the
loop and resume layout of the panel when the loop is over
That's not what SuspendLayout and ResumeLayout are for. They suspend the layout logic, that is, the automatic positioning of the controls. Most relevant with FlowLayoutPanel and TableLayoutPanel.
As for doublebuffering, I'm not sure it applies to custom draw code (haven't tried). I guess you should implement your own.
Doublebuffering in a nutshell:
It's very simple, a couple lines of code. On the paint event, render to a bitmap instead of rendering to the Graphics object, and then draw that bitmap to the Graphics object.

In addition to the DoubleBuffered property, also try adding this to your control's constructor:
SetStyle(ControlStyles.OptimizedDoubleBuffer |
ControlStyles.AllPaintingInWmPaint, true);
And if that ends up not being enough (which I'm gonna go out on a limb and say it isn't), consider having a look at my answer to this question and suspend/resume the redraw of the panel or Form. This would let your layout operations complete, then do all of the drawing once that's done.

You may want to look at the answer to my question, How do I suspend painting for a control and its children? for a better Suspend/Resume.

It sounds like what you are looking for is a "composited" display, where the entire application is drawn all at once, almost like one big bitmap. This is what happens with WPF applications, except the "chrome" surrounding the application (things like the title bar, resize handles and scrollbars).
Note that normally, unless you've messed with some of the window styles, each Windows Form control is responsible for painting itself. That is, every control gets a crack at the WM_ PAINT, WM_ NCPAINT, WM_ERASEBKGND, etc painting related messages and handles these message independently. What this means for you is that double buffering only applies to the single control you are dealing with. To get somewhat close to a clean, composited effect, you need to concern yourself not just with your custom controls that you are drawing, but also the container controls on which they are placed. For example, if you have a Form that contains a GroupBox which in turn contains a number of custom drawn buttons, each of these controls should have there DoubleBuffered property set to True. Note that this property is protected, so this means you either end up inheriting for the various controls (just to set the double buffering property) or you use reflection to set the protected property. Also, not all Windows Form controls respect the DoubleBuffered property, as internally some of them are just wrappers around the native "common" controls.
There is a way to set a composited flag if you are targeting Windows XP (and presumably later). There is the WS_ EX_ COMPOSITED window style. I have used it before to mix results. It doesn't work well with WPF/WinForm hybrid applications and also does not play well with the DataGridView control. If you go this route, be sure you do lots of testing on different machines because I've seen strange results. In the end, I abandoned used of this approach.

Maybe first draw on a control-only 'visible' (private) buffer and then render it:
In your control
BufferedGraphicsContext gfxManager;
BufferedGraphics gfxBuffer;
Graphics gfx;
A function to install graphics
private void InstallGFX(bool forceInstall)
{
if (forceInstall || gfxManager == null)
{
gfxManager = BufferedGraphicsManager.Current;
gfxBuffer = gfxManager.Allocate(this.CreateGraphics(), new Rectangle(0, 0, Width, Height));
gfx = gfxBuffer.Graphics;
}
}
In its paint method
protected override void OnPaint(PaintEventArgs e)
{
InstallGFX(false);
// .. use GFX to draw
gfxBuffer.Render(e.Graphics);
}
In its resize method
protected override void OnSizeChanged(EventArgs e)
{
base.OnSizeChanged(e);
InstallGFX(true); // To reallocate drawing space of new size
}
The code above has been somewhat tested.

I had the same problem with a tablelayoutpanel when switching usercontrols that I wanted displayed.
I completely got rid of the flicker by creating a class that inherited the table, then enabled doublebuffering.
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
namespace myNameSpace.Forms.UserControls
{
public class TableLayoutPanelNoFlicker : TableLayoutPanel
{
public TableLayoutPanelNoFlicker()
{
this.DoubleBuffered = true;
}
}
}

I've had a lot of similar issues in the past, and the way I resolved it was to use a third-party UI suite (that is, DevExpress) rather than the standard Microsoft controls.
I started out using the Microsoft standard controls, but I found that I was constantly debugging issues which were caused by their controls. The problem is made worse by the fact that Microsoft generally does not fix any of the issues which are identified and they do very little to provide suitable workarounds.
I switched to DevExpress, and I have nothing but good things to say. The product is solid, they provide great support and documentation and yes they actually listen to their customers. Any time I had a question or an issue, I got a friendly response within 24 hours. In a couple of cases, I did find a bug and in both instances, they implemented a fix for the next service release.

I have seen bad winforms flicker on forms where the controls referred to a missing font.
This is probably not common, but it's worth looking into if you've tried everything else.

WPF - ScreenSaver graphics performance improvements

I took this WPF-VS2008 ScreenSaver template and started to make a new screen saver. I have some experience with winForms-platform (GDI+) screen savers, so i am little bit lost with WPF.
Background-element for my screen saver is Canvas.
A DispatcherTimer tick is set to 33 msec, which is ~ 30 FPS.
Background-color is just one huge LinearGradientBrush.
On the screen I have (per available screen, on my local computer i have 2) n-Ellipses drawn with randomly-calculated (Initialization) Background colors + Alpha channel. They are all in Canvas's Children collection.
I'm moving those Ellipses around the screen with some logic (every DispatcherTimer tick). I make a move per-ellipse, and then just call Canvas.SetLeft(...) and Canvas.SetTop(...) for each Ellipse.
If N (number of Ellipses) is higher > 70-80, i begin to notice graphics slow-downs.
Now, i wonder, if there is anything i could do to improve the graphic-smoothness when choosing higher N-values ? Can I "freeze" "something" before moving my Ellipses and "un-freeze" "something" when i'm finished ? Or is there any other trick i could do?
Not that i would be too picky about mentioned performance drop downs - becouse when N==50, everything works smooth as it should. Even if Ellipses are ALL in the SAME place (loads of transparency stuff), there are no problems at all.

Have you tried rendering in the CompositionTarget.Rendering event, rather than in a timer? I've gotten impressive performance in a 3D screen saver when using the Rendering event and doing my own double buffering. (See http://stuff.seans.com/2008/08/21/simple-water-animation-in-wpf/ , http://stuff.seans.com/2008/08/24/raindrop-animation-in-wpf/ , and http://stuff.seans.com/2008/09/01/writing-a-screen-saver-in-wpf/ )

You will improve performance if you call the Freeze method on objects that inherit from Freezable - brushes for example.
The reason is that Freezable supports extra change notifications that have to be handled by the graphics system, when you call Freeze the object can no longer change and so there are no more change notifications.
For an example of this notification system, if you create a brush, use it to paint a rectangle (for example) and then change the brush the on-screen rectangle will change color.

It is not possible to unfreeze something once it has been frozen (although a copy of the object is unfozen by default). Double buffering is also enabled by default in WPF so you cannot gain here.
Once way to improve performance if not already done is to use geometry objects such as Ellipse Geometry rather than shapes if you do not need to the all of the events as these are lighter weight.
I also have found this MSDN Article Optimizing Performance: 2D Graphics and Imaging that suggests a CachingHint may help along with some other tips.
Finally ensure that you are using the latest service pack one as it has many performance improvements outlined here