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dotnet drawing api : How to draw to the screen not the form?
(unfilled) to the screen's area, not a form or window area. I am trying to simulate a technique I have seen when a new window opens, a series of ever-larger rectangles are drawn to give a dynamic confirmation that the form is opening. The rectangles increase in size until they have reached the size of the form being opened, then the form is finally displayed and the rectangles are removed. I want to add this to an application I am writing so that when a form is opened, this dynamic feedback will be shown. In order to do this, I have to be able to draw the rectangles to the screen, not the current form since the form that is about to be opened can be well outside the boundaries of the parent form. Does anyone know how to do this?
A clue to the solution would be GetDC(IntPtr.Zero) in order to obtain a device context to the screen.. There is a sample here, drawing a filled ellipse on the screen: http://www.thescripts.com/forum/thread263740.html For drawing the rectangles, you need to look at some of the usual rubber-band code floating around, such as http://www.codeproject.com/cs/media/MixedRubberBandApp1.asp In other words, use the XORPEN flag to draw it, then draw it again using XORPEN to remove it. But more importantly: You shouldn't do it. You do not know (I suppose you could find out) what theme is enabled on the user's desktop, e.g. whether Vista Aero or some other animation effect is already enabled for forms as standard, so you would be interferring with the system possibly end up with something ugly, e.g. rectangles not properly removed because the system was drawing to the same area as your code. I suppose this would not be a problem if you drew the animation before attempting to show the form, which I presume would be the case. Even more importantly: Before you start working on something like this, read this blog post: http://blogs.msdn.com/greg_schechter/archive/2006/05/02/588934.aspx esp. the section "Drawing To and Reading From the Screen -- Baaaad!" /Joergen Bech On 25 Oct 2006 14:27:16 -0700, "cheapguy" <bmwm3e36@bellsouth.net> [quoted text, click to view] wrote:
>I need some code (VB or C#) that will draw a series of rectangles >(unfilled) to the screen's area, not a form or window area. I am trying >to simulate a technique I have seen when a new window opens, a series >of ever-larger rectangles are drawn to give a dynamic confirmation that >the form is opening. The rectangles increase in size until they have >reached the size of the form being opened, then the form is finally >displayed and the rectangles are removed. I want to add this to an >application I am writing so that when a form is opened, this dynamic >feedback will be shown. In order to do this, I have to be able to draw >the rectangles to the screen, not the current form since the form that >is about to be opened can be well outside the boundaries of the parent >form. Does anyone know how to do this?
Just use ControlPaint.DrawReversiblexxx. That draws directly on the desktop
and can draw outside of windows etc. -- Bob Powell [MVP] Visual C#, System.Drawing Ramuseco Limited .NET consulting http://www.ramuseco.com Find great Windows Forms articles in Windows Forms Tips and Tricks http://www.bobpowell.net/tipstricks.htm Answer those GDI+ questions with the GDI+ FAQ http://www.bobpowell.net/faqmain.htm All new articles provide code in C# and VB.NET. Subscribe to the RSS feeds provided and never miss a new article. [quoted text, click to view] "cheapguy" <bmwm3e36@bellsouth.net> wrote in message news:1161811636.621757.245340@f16g2000cwb.googlegroups.com... >I need some code (VB or C#) that will draw a series of rectangles > (unfilled) to the screen's area, not a form or window area. I am trying > to simulate a technique I have seen when a new window opens, a series > of ever-larger rectangles are drawn to give a dynamic confirmation that > the form is opening. The rectangles increase in size until they have > reached the size of the form being opened, then the form is finally > displayed and the rectangles are removed. I want to add this to an > application I am writing so that when a form is opened, this dynamic > feedback will be shown. In order to do this, I have to be able to draw > the rectangles to the screen, not the current form since the form that > is about to be opened can be well outside the boundaries of the parent > form. Does anyone know how to do this? >
Yes, that function does the same (although one is limited to two styles then). But the thing is: It still obtains/releases a handle to the desktop DC under the covers. I understood from the article I linked to in my previous post (http://blogs.msdn.com/greg_schechter/archive/2006/05/02/588934.aspx) that you should avoid writing to/reading from the screen (at least for something as realtime as this, though a screen capture program would be ok)? I have a component where I currently draw some selection rectangles directly on the screen (which is similar in nature to what the original poster is attempting). Trouble is: When I run this on Vista with Aero enabled, dragging those rectangles around happen at a few frames a second, whereas it runs smooth on XP (or Vista with the standard, non-Aero theme). Wouldn't the original poster have the same problem if using ControlPaint.DrawReversible...? I have considered solving my own problem this way: 1. On MouseDown, grab a snapshot containing the portion of the screen my interface occupies. Only one desktop GetDC required. 2. Put this snapshot on an overlay and display this on top of my interface. 3. On MouseMove, draw my rectangles on the overlay. 4. On MouseUp, remove the overlay. This would make the rectangles part of my application and would not constantly force Vista in and out of DirectX10. I am not convinced that ControlPaint.DrawReversible... is as appropriate today as it has been in the past. Also remember that this method *only* draws on the desktop. If you need to draw such rectangles on other device contexts, you have to implement it yourself. Any thoughts? /Joergen Bech On Thu, 26 Oct 2006 12:52:19 +0200, "Bob Powell [MVP]" [quoted text, click to view] <bob@_spamkiller_.bobpowell.net> wrote:
>Just use ControlPaint.DrawReversiblexxx. That draws directly on the desktop >and can draw outside of windows etc.
Hmm, I hadn't considered the Vista implications.
Maybe it'd be best to look at the Windows version and use the method best suited to the technology. On XP ControlPaint is fine. -- Bob Powell [MVP] Visual C#, System.Drawing Ramuseco Limited .NET consulting http://www.ramuseco.com Find great Windows Forms articles in Windows Forms Tips and Tricks http://www.bobpowell.net/tipstricks.htm Answer those GDI+ questions with the GDI+ FAQ http://www.bobpowell.net/faqmain.htm All new articles provide code in C# and VB.NET. Subscribe to the RSS feeds provided and never miss a new article. [quoted text, click to view] "Joergen Bech @ post1.tele.dk>" <jbech<NOSPAMNOSPAM> wrote in message news:sr61k2le8id3qfl98o67pg5e5em2f3gpj6@4ax.com... > > Yes, that function does the same (although one is limited > to two styles then). > > But the thing is: It still obtains/releases a handle to the > desktop DC under the covers. I understood from the article > I linked to in my previous post > (http://blogs.msdn.com/greg_schechter/archive/2006/05/02/588934.aspx) > that you should avoid writing to/reading from the screen (at > least for something as realtime as this, though a screen capture > program would be ok)? > > I have a component where I currently draw some selection > rectangles directly on the screen (which is similar in nature to > what the original poster is attempting). Trouble is: When I run > this on Vista with Aero enabled, dragging those rectangles around > happen at a few frames a second, whereas it runs smooth > on XP (or Vista with the standard, non-Aero theme). > > Wouldn't the original poster have the same problem if using > ControlPaint.DrawReversible...? > > I have considered solving my own problem this way: > > 1. On MouseDown, grab a snapshot containing the portion of the screen > my interface occupies. Only one desktop GetDC required. > > 2. Put this snapshot on an overlay and display this on top of my > interface. > > 3. On MouseMove, draw my rectangles on the overlay. > > 4. On MouseUp, remove the overlay. > > This would make the rectangles part of my application and would > not constantly force Vista in and out of DirectX10. > > I am not convinced that ControlPaint.DrawReversible... > is as appropriate today as it has been in the past. Also remember that > this method *only* draws on the desktop. If you need to draw such > rectangles on other device contexts, you have to implement it > yourself. > > Any thoughts? > > /Joergen Bech > > > > On Thu, 26 Oct 2006 12:52:19 +0200, "Bob Powell [MVP]" > <bob@_spamkiller_.bobpowell.net> wrote: > >>Just use ControlPaint.DrawReversiblexxx. That draws directly on the >>desktop >>and can draw outside of windows etc. >
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