So I Tried Graphics Tonight For The First Time
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Som Shekhar wrote:
Dispose the graphics object after you are done with it. This is a major source of memory leak.
I've never heard that. Why would the Graphics object be a source for a memory leak?
aspdotnetdev wrote:
Why would the Graphics object be a source for a memory leak?
Because it's using unmanaged resources (GDI+).
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
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Som Shekhar wrote:
Dispose the graphics object after you are done with it. This is a major source of memory leak.
I've never heard that. Why would the Graphics object be a source for a memory leak?
This gets a little complex, but: The Graphics object is a limited resource, which contains unmanaged memory. What that means is that it uses memory which is not on the normal C# heap, or the stack - it is in a different area completely, and the .NET garbage collector will not process it. When your method ends, the last reference to the object is destroyed, so it becomes available to be garbage collected - which is fine. But, the GC will only try to dispose of it when it runs short of managed memory - which could be in a few weeks time, you just don't know! In the meantime, all that unused, unmanaged memory is sitting there, being wasted. If you manually call Dispose() on your object when you are finished with it, the resources are released immediately, and all is well. The easiest way to do this is to wrap you object in a
usingblock:using(Graphics g = CreateGraphics())
{
... use the Graphics object
}The system will then call Dispose at the end. I probably haven't explained this too well, but if you look in any reasonable book on C#, it will talk about it in loads more detail! BTW: I wouldn't do the drawing in the Button.Click event - do it in the Form.Paint event - which supplies you with a graphics context in e.Graphics - and use the Button.Click to set any parameters (such as where you want it, what color, etc.) then call Invalidate() to force a re-draw.
I have learnt that you can not make someone love you, all you can do is stalk them and hope they panic and give in. Apathy Error: Don't bother striking any key.
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This gets a little complex, but: The Graphics object is a limited resource, which contains unmanaged memory. What that means is that it uses memory which is not on the normal C# heap, or the stack - it is in a different area completely, and the .NET garbage collector will not process it. When your method ends, the last reference to the object is destroyed, so it becomes available to be garbage collected - which is fine. But, the GC will only try to dispose of it when it runs short of managed memory - which could be in a few weeks time, you just don't know! In the meantime, all that unused, unmanaged memory is sitting there, being wasted. If you manually call Dispose() on your object when you are finished with it, the resources are released immediately, and all is well. The easiest way to do this is to wrap you object in a
usingblock:using(Graphics g = CreateGraphics())
{
... use the Graphics object
}The system will then call Dispose at the end. I probably haven't explained this too well, but if you look in any reasonable book on C#, it will talk about it in loads more detail! BTW: I wouldn't do the drawing in the Button.Click event - do it in the Form.Paint event - which supplies you with a graphics context in e.Graphics - and use the Button.Click to set any parameters (such as where you want it, what color, etc.) then call Invalidate() to force a re-draw.
I have learnt that you can not make someone love you, all you can do is stalk them and hope they panic and give in. Apathy Error: Don't bother striking any key.
Wise men have already spoken. So, no need to answer the question asked about disposing. Your suggestion is right about doing the paint part in Form.Paint event. However, I don't see anything wrong in doing it in Button_Click for learning purposes. Doing all drawing during paint may become an herculean task. I prefer doing my drawing on a bitmap at different occasions and draw the bitmap during Form.Paint. This imitates double buffering and saves from doing any calculations that may be required in Form.Paint every time the form is painted.
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Big mistake... I've avoided it for decades, as Windows makes it so hard to do - at least through the eyes of a tyro. But it's time I learned it, and I sat down tonight intending to do so. I thought I'd start with drawing a simple circle on a form, and searching in Help returned a likely bit with sample code for drawing a rectangle and a circle within it, along with a button_Click handler to call the drawing function. I copied and pasted the sample code into my 800x600 form, just to try it out. Then I added a button1 object to provide the event. The code is:
public partial class FlowCalcs : Form
{
public FlowCalcs()
{
InitializeComponent();
}
private void DrawIt()
{
System.Drawing.Graphics graphics = this.CreateGraphics();
System.Drawing.Rectangle rectangle = new System.Drawing.Rectangle(
100, 100, 200, 200);
graphics.DrawEllipse(System.Drawing.Pens.Black, rectangle);
graphics.DrawRectangle(System.Drawing.Pens.Red, rectangle);
}
private void button1_Click(object sender, EventArgs e)
{
DrawIt();
}
}When I debugged it, absolutely nothing happened - no rectangle, no circle, and no errors. I would welcome an error message, since occasionally Microsoft divulges some tiny bit of information that Google can find a solution for. But no such luck this time - it executes perfectly and does nothing. Can someone lend a clue to the clueless? I haven't any idea where to go next...
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
Hi Roger, All the advice you've been given is correct. I just thought I'd put my 2c in...
Graphicsobjects,Pens &Brushes should be disposed of unless they are available already as a property/parameter. If you draw in OnPaint you can use thee.Graphicsproperty and there is no need to dispose it. If however you are drawing elsewhere and usingCreateGraphicsthen you should dispose of it either explicitly, or implicitly by using ausingblock. The same forPens andBrushes, if you are using the System ones as in your code then there is no need to dispose, but if you create your own then you must dispose of them. If it's a one off drawing I normally drop it into theOnPainthandler as has been suggested. If it's likely to be used several times I create a class/struct with aDrawmethod that takes any useful parameters including aGraphicsinstance and call that fromOnPaint. TriggeringOnPaintis easily done by callingInvalidate. Something like this gives you a reusable Rectangle/Ellipse that can be drawn easily and no memory leaks.using System;
using System.Drawing;
using System.Windows.Forms;public partial class FormFlowCalcs : Form
{
private RectangleWithEllipseUnfilled rectangleWithEllipseUnfilled;
private Point rectangleWithEllipseUnfilledLocation;
private bool rectangleWithEllipseUnfilledVisible;public FormFlowCalcs() { InitializeComponent(); Size = new Size(800, 600); rectangleWithEllipseUnfilled = new RectangleWithEllipseUnfilled( Color.Black, Color.Red, new Size(200, 200)); rectangleWithEllipseUnfilledLocation = new Point(200, 200); rectangleWithEllipseUnfilledVisible = false; } private void buttonToggle\_Click(object sender, EventArgs e) { rectangleWithEllipseUnfilledVisible = !rectangleWithEllipseUnfilledVisible; Invalidate(); } protected override void OnPaint(PaintEventArgs e) { base.OnPaint(e); if (rectangleWithEllipseUnfilledVisible) rectangleWithEllipseUnfilled.Draw(rectangleWithEllipseUnfilledLocation, e.Graphics); }}
public struct RectangleWithEllipseUnfilled
{
private Color ellipseColor;
private Color rectangleColor;
private Size size;public RectangleWithEllipseUnfilled(Color ell -
Wise men have already spoken. So, no need to answer the question asked about disposing. Your suggestion is right about doing the paint part in Form.Paint event. However, I don't see anything wrong in doing it in Button_Click for learning purposes. Doing all drawing during paint may become an herculean task. I prefer doing my drawing on a bitmap at different occasions and draw the bitmap during Form.Paint. This imitates double buffering and saves from doing any calculations that may be required in Form.Paint every time the form is painted.
While Pete had explained that dispose should be used, he hadn't explained why, or how to best do it. I felt it worth a (slightly) more detailed response. The only problem with drawing in the Click event for learning purposes is that it can confuse more than elucidate - look at the number of "I drew it and it disappeared" questions we get. Starting off with drawing into the Paint event, with an existing Graphics context just makes it a bit easier for beginners. They can them be introduced to the concept of graphics contexts for other objects. :-D
I have learnt that you can not make someone love you, all you can do is stalk them and hope they panic and give in. Apathy Error: Don't bother striking any key.
-
While Pete had explained that dispose should be used, he hadn't explained why, or how to best do it. I felt it worth a (slightly) more detailed response. The only problem with drawing in the Click event for learning purposes is that it can confuse more than elucidate - look at the number of "I drew it and it disappeared" questions we get. Starting off with drawing into the Paint event, with an existing Graphics context just makes it a bit easier for beginners. They can them be introduced to the concept of graphics contexts for other objects. :-D
I have learnt that you can not make someone love you, all you can do is stalk them and hope they panic and give in. Apathy Error: Don't bother striking any key.
Hey, lemme say sorry for not writing in the correct grammar. What i said was:
Som wrote:
Wise men have already spoken. So, no need to answer the question asked about disposing.
and what i meant
Wise men have already spoken. So, I do not need to answer the question asked about disposing.he he he. I was talking about both of you. I do not deny that writing in Paint event is incorrect. I am only saying that it is not necessary and shouldn't be considered as a norm. Thats all. By the way, our so long discussion might be confusing the poor guy who wrote the code for the first time :laugh: -
Big mistake... I've avoided it for decades, as Windows makes it so hard to do - at least through the eyes of a tyro. But it's time I learned it, and I sat down tonight intending to do so. I thought I'd start with drawing a simple circle on a form, and searching in Help returned a likely bit with sample code for drawing a rectangle and a circle within it, along with a button_Click handler to call the drawing function. I copied and pasted the sample code into my 800x600 form, just to try it out. Then I added a button1 object to provide the event. The code is:
public partial class FlowCalcs : Form
{
public FlowCalcs()
{
InitializeComponent();
}
private void DrawIt()
{
System.Drawing.Graphics graphics = this.CreateGraphics();
System.Drawing.Rectangle rectangle = new System.Drawing.Rectangle(
100, 100, 200, 200);
graphics.DrawEllipse(System.Drawing.Pens.Black, rectangle);
graphics.DrawRectangle(System.Drawing.Pens.Red, rectangle);
}
private void button1_Click(object sender, EventArgs e)
{
DrawIt();
}
}When I debugged it, absolutely nothing happened - no rectangle, no circle, and no errors. I would welcome an error message, since occasionally Microsoft divulges some tiny bit of information that Google can find a solution for. But no such luck this time - it executes perfectly and does nothing. Can someone lend a clue to the clueless? I haven't any idea where to go next...
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
Hi Roger, I agree with what the others have said. And I add an example[^] that contains the relevant bits. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
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Hi Roger, I agree with what the others have said. And I add an example[^] that contains the relevant bits. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
Now I remember why I gave up trying to do any graphics work when Windows came out. :sigh:
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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Wise men have already spoken. So, no need to answer the question asked about disposing. Your suggestion is right about doing the paint part in Form.Paint event. However, I don't see anything wrong in doing it in Button_Click for learning purposes. Doing all drawing during paint may become an herculean task. I prefer doing my drawing on a bitmap at different occasions and draw the bitmap during Form.Paint. This imitates double buffering and saves from doing any calculations that may be required in Form.Paint every time the form is painted.
Som Shekhar wrote:
I don't see anything wrong in doing it in Button_Click for learning purposes
For the most part yes, but many beginners get the idea that that is a "best practice" and never progress -- much like all the books that show data access in click handlers.
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Hi Roger, I agree with what the others have said. And I add an example[^] that contains the relevant bits. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
Hey Luc, Is there any Graphics Library available for .Net which does more than what GDI+ does? I mean something that takes care of some advanced functions like layering? I have an interest in printing multiple png images with transparency, being able to drag and drop them. Also, having multiple layers like in Adobe Photoshop? Ofcourse I mean open source/free. Som
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Big mistake... I've avoided it for decades, as Windows makes it so hard to do - at least through the eyes of a tyro. But it's time I learned it, and I sat down tonight intending to do so. I thought I'd start with drawing a simple circle on a form, and searching in Help returned a likely bit with sample code for drawing a rectangle and a circle within it, along with a button_Click handler to call the drawing function. I copied and pasted the sample code into my 800x600 form, just to try it out. Then I added a button1 object to provide the event. The code is:
public partial class FlowCalcs : Form
{
public FlowCalcs()
{
InitializeComponent();
}
private void DrawIt()
{
System.Drawing.Graphics graphics = this.CreateGraphics();
System.Drawing.Rectangle rectangle = new System.Drawing.Rectangle(
100, 100, 200, 200);
graphics.DrawEllipse(System.Drawing.Pens.Black, rectangle);
graphics.DrawRectangle(System.Drawing.Pens.Red, rectangle);
}
private void button1_Click(object sender, EventArgs e)
{
DrawIt();
}
}When I debugged it, absolutely nothing happened - no rectangle, no circle, and no errors. I would welcome an error message, since occasionally Microsoft divulges some tiny bit of information that Google can find a solution for. But no such luck this time - it executes perfectly and does nothing. Can someone lend a clue to the clueless? I haven't any idea where to go next...
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
I tried a little of that a while back, and found it not to be as straight-forward as I had hoped. I only needed to draw some lines and I got it working.
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Now I remember why I gave up trying to do any graphics work when Windows came out. :sigh:
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
Really? I don't find it hard at all, and Windows does a lot of things for you. You don't have to care about windows being partly hidden, getting uncovered, minimized, etc. It will repaint for you, assuming you did it right to start with. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
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I tried a little of that a while back, and found it not to be as straight-forward as I had hoped. I only needed to draw some lines and I got it working.
Then don't stop; the first line is the hardest :laugh:
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
-
Hey Luc, Is there any Graphics Library available for .Net which does more than what GDI+ does? I mean something that takes care of some advanced functions like layering? I have an interest in printing multiple png images with transparency, being able to drag and drop them. Also, having multiple layers like in Adobe Photoshop? Ofcourse I mean open source/free. Som
I'm not experienced with any additional library, I tend to write the code I use myself. Mostly from reading forums like this one, I must warn you transparancy is a bit tricky in Windows. You may want to look to some of the graphics articles at CodeProject; and then there is GIMP which could inspire you. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
-
Then don't stop; the first line is the hardest :laugh:
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
naah.. the hardest part is to fight flickering ;) when anything u do in windows doesn't work :D
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While Pete had explained that dispose should be used, he hadn't explained why, or how to best do it. I felt it worth a (slightly) more detailed response. The only problem with drawing in the Click event for learning purposes is that it can confuse more than elucidate - look at the number of "I drew it and it disappeared" questions we get. Starting off with drawing into the Paint event, with an existing Graphics context just makes it a bit easier for beginners. They can them be introduced to the concept of graphics contexts for other objects. :-D
I have learnt that you can not make someone love you, all you can do is stalk them and hope they panic and give in. Apathy Error: Don't bother striking any key.
He wasn't talking about me. He said wise. ;) Good explanation though and you might want to consider posting it as a tip/trick so that it can be easily linked to in response to other questions.
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
-
Hey Luc, Is there any Graphics Library available for .Net which does more than what GDI+ does? I mean something that takes care of some advanced functions like layering? I have an interest in printing multiple png images with transparency, being able to drag and drop them. Also, having multiple layers like in Adobe Photoshop? Ofcourse I mean open source/free. Som
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I'm not experienced with any additional library, I tend to write the code I use myself. Mostly from reading forums like this one, I must warn you transparancy is a bit tricky in Windows. You may want to look to some of the graphics articles at CodeProject; and then there is GIMP which could inspire you. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
GIMP is what drove me to try drawing in Windows. :-O
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
-
Then don't stop; the first line is the hardest :laugh:
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
Just don't go one toke over the line.
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naah.. the hardest part is to fight flickering ;) when anything u do in windows doesn't work :D
The hardest part was keeping them where I want them as the underlying control scrolls, horizontally and vertically. :sigh:
