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Draw Line of Form?Can draw a line on my form with a button click event but cannot upon the
Load event when I wish. No more line object so used the following: Dim bit As Bitmap = New Bitmap(Me.Width, Me.Height) Dim g As Graphics = Graphics.FromImage(bit) Dim myPen As Pen = New Pen(Color.Blue, 1) Me.CreateGraphics.DrawLine(myPen, 0, 5, Me.Width, 5) Appreciate some help. Ed Ed,
"Ed Bitzer" <edbit***@yahoo.com> schrieb: At the time when the form's 'Load' event is raised, the form is not yet > Can draw a line on my form with a button click event but cannot upon the > Load event when I wish. No more line object so used the following: > Dim bit As Bitmap = New Bitmap(Me.Width, Me.Height) > Dim g As Graphics = Graphics.FromImage(bit) > Dim myPen As Pen = New Pen(Color.Blue, 1) > Me.CreateGraphics.DrawLine(myPen, 0, 5, Me.Width, 5) visible. Thus the drawing will not be visible when the form is shown. In ..NET's drawing model, drawings need to be renewed whenever a part of the form which is obscured gets visible again. You may want to place your drawing code in the form's 'Paint' event handler or an overridden 'OnPaint' method. These methods will be called whenever a part of the form needs to be redrawn: \\\ Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs) MyBase.OnPaint(e) e.Graphics.DrawLine(Pens.Blue, 0, 5, Me.Width, 5) End Sub /// Don't fotget to call the 'Dispose' method of 'Graphics' and 'Pen' objects you created yourself ('CreateGraphics', 'New Pen(...)') when you don't need them any more. -- M S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://classicvb.org/petition/> > Doesn't the Garbage Collector handle this sort of thing once they go out of > Don't fotget to call the 'Dispose' method of 'Graphics' and 'Pen' objects > you created yourself ('CreateGraphics', 'New Pen(...)') when you don't > need them any more. > scope? Apologies if this is a silly question. Martin. Martin,
"Martin Horn" <mvh***@notThisBit.ntlworld.com> schrieb: ..NET doesn't support deterministic finalization of objects as known from >> Don't fotget to call the 'Dispose' method of 'Graphics' and 'Pen' objects >> you created yourself ('CreateGraphics', 'New Pen(...)') when you don't >> need them any more. > > Doesn't the Garbage Collector handle this sort of thing once they go out > of scope? Apologies if this is a silly question. COM/VB6. The GC will destroy the object, but this will not occur immediately when all reachable references to the object are released. 'Graphics' and 'Pen' use unmanaged resources (GDI handles). By calling 'Dispose' directly these resources are released immediately, which can prevent the application from missing unmanaged resources. -- M S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://classicvb.org/petition/> Herfried,
Understand and as indicated if I place in the Paint event I the lines are displayed. Of course I tried to extrapolate my new knowledge but was not able to use the same logic with a PictureBox. If I add a PictureBox to the load event on my form and then try to draw lines using the same approach placing the line drawing code in the PictureBox even - no work. I of course did change all references to Me in the Form example to PictureBox. Is that as simply explainable? Ed Show quoteHide quote "Herfried K. Wagner [MVP]" <hirf-spam-me-here@gmx.at> wrote in message news:O%23Is0IFOFHA.3880@tk2msftngp13.phx.gbl... > Ed, > > "Ed Bitzer" <edbit***@yahoo.com> schrieb: >> Can draw a line on my form with a button click event but cannot upon the >> Load event when I wish. No more line object so used the following: >> Dim bit As Bitmap = New Bitmap(Me.Width, Me.Height) >> Dim g As Graphics = Graphics.FromImage(bit) >> Dim myPen As Pen = New Pen(Color.Blue, 1) >> Me.CreateGraphics.DrawLine(myPen, 0, 5, Me.Width, 5) > > > At the time when the form's 'Load' event is raised, the form is not yet > visible. Thus the drawing will not be visible when the form is shown. In > .NET's drawing model, drawings need to be renewed whenever a part of the > form which is obscured gets visible again. You may want to place your > drawing code in the form's 'Paint' event handler or an overridden > 'OnPaint' method. These methods will be called whenever a part of the > form needs to be redrawn: > > \\\ > Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs) > MyBase.OnPaint(e) > e.Graphics.DrawLine(Pens.Blue, 0, 5, Me.Width, 5) > End Sub > /// > > Don't fotget to call the 'Dispose' method of 'Graphics' and 'Pen' objects > you created yourself ('CreateGraphics', 'New Pen(...)') when you don't > need them any more. > > -- > M S Herfried K. Wagner > M V P <URL:http://dotnet.mvps.org/> > V B <URL:http://classicvb.org/petition/> Ed,
"Ed Bitzer" <edbit***@yahoo.com> schrieb: I assume that you took the 'OnPaint' code I posted and tried to use it for a > Understand and as indicated if I place in the Paint event I the lines are > displayed. Of course I tried to extrapolate my new knowledge but was not > able to use the same logic with a PictureBox. If I add a PictureBox to > the load event on my form and then try to draw lines using the same > approach placing the line drawing code in the PictureBox even - no work. > I of course did change all references to Me in the Form example to > PictureBox. Is that as simply explainable? picturebox placed on a form. This won't work, because 'OnPaint' is a protected method that can only be overridden in a class that derives from the base class containing this method. So, there are two solutions: Simple solution: Instead of overriding 'OnPaint', simply add a handler to the picturebox's 'Paint' event. To do that, open the code editor window, choose the picturebox from the left combobox (which is on top of the code editor) and select 'Paint' in the combobox on the right side. An event handler will be generated automatically. All you need to do is simply entering your drawing code in the event handler. Complicated solution: Create a new class that inherits from 'PictureBox' and overrides its 'OnPaint' method. Then use this extended picturebox class instead of the standard picturebox control. -- M S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://classicvb.org/petition/> Herfried,
You do more than yeoman's work for this forum and I do appreciate the tutoring. I will drag out one more round. I did not see you OnPaint but just blindly dove in. I have tried the PictureBox again selecting PictureBox and then Paint as suggested - the following code does nothing. If I replace PictureBox1 with Me.CreateGraphics, it draws on the form but behind the PictureBox. Does that follow the rules ? Sure would love to have it draw on the PictureBox Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint Dim c, i As Short Dim inc As Short Dim bit As Bitmap = New Bitmap(PictureBox1.Width, PictureBox1.Height) Dim g As Graphics = Graphics.FromImage(bit) Dim myPen As Pen = New Pen(Color.Red, 1) c = 10 inc = 20 For i = 0 To 30 PictureBox1.CreateGraphics.DrawLine(myPen, PictureBox1.Left, c + i * inc, PictureBox1.Width, c + i * inc) Next myPen.Dispose() g.Dispose() End Sub Ed Show quoteHide quote "Herfried K. Wagner [MVP]" <hirf-spam-me-here@gmx.at> wrote in message news:OJX0biVOFHA.2144@TK2MSFTNGP09.phx.gbl... > I assume that you took the 'OnPaint' code ............... > Simple solution: Instead of overriding 'OnPaint', simply add a handler to > the picturebox's 'Paint' event. To do that, open the code editor window, > choose the picturebox from the left combobox (which is on top of the code > editor) and select 'Paint' in the combobox on the right side. An event > handler will be generated automatically. All you need to do is simply > entering your drawing code in the event handler. > > M S Herfried K. Wagner Ed,
"Ed Bitzer" <edbit***@yahoo.com> schrieb: Well, yes, because you are retreiving a 'Graphics' object for the /form/ and > You do more than yeoman's work for this forum and I do appreciate the > tutoring. I will drag out one more round. I did not see you OnPaint but > just blindly dove in. I have tried the PictureBox again selecting > PictureBox and then Paint as suggested - the following code does nothing. > If I replace PictureBox1 with Me.CreateGraphics, it draws on the form but > behind the PictureBox. Does that follow the rules ? not the picturebox. > Sure would love to have it draw on the PictureBox I suggest not to use 'CreateGraphics'. Instead, you can access the 'Graphics' object for the picturebox in the 'e' parameter of your 'Paint' event handler ('e.Graphics'). > Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As Replace 'PictureBox1.CreateGraphics.DrawLine' with 'e.DrawLine'. This > System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint > Dim c, i As Short > Dim inc As Short > Dim bit As Bitmap = New Bitmap(PictureBox1.Width, PictureBox1.Height) > Dim g As Graphics = Graphics.FromImage(bit) > Dim myPen As Pen = New Pen(Color.Red, 1) > c = 10 > inc = 20 > For i = 0 To 30 > PictureBox1.CreateGraphics.DrawLine(myPen, PictureBox1.Left, c + i * should solve the problem. -- M S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://classicvb.org/petition/> Herfried,
And it does as advertised. I just to have to get a third book to learn my fundamentals so that I can use the help system which truly is extensive - you just have to have the fundamentals down first. Glad I don't do this for a living<g>. I do thank you, Ed Show quoteHide quote "Herfried K. Wagner [MVP]" <hirf-spam-me-here@gmx.at> wrote in message news:e9a3MPhOFHA.3928@TK2MSFTNGP09.phx.gbl... > Ed, > > "Ed Bitzer" <edbit***@yahoo.com> schrieb: >> You do more than yeoman's work for this forum and I do appreciate the >> tutoring. I will drag out one more round. I did not see you OnPaint but >> just blindly dove in. I have tried the PictureBox again selecting >> PictureBox and then Paint as suggested - the following code does nothing. >> If I replace PictureBox1 with Me.CreateGraphics, it draws on the form but >> behind the PictureBox. Does that follow the rules ? > > Well, yes, because you are retreiving a 'Graphics' object for the /form/ > and not the picturebox. > >> Sure would love to have it draw on the PictureBox > > I suggest not to use 'CreateGraphics'. Instead, you can access the > 'Graphics' object for the picturebox in the 'e' parameter of your 'Paint' > event handler ('e.Graphics'). > >> Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As >> System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint >> Dim c, i As Short >> Dim inc As Short >> Dim bit As Bitmap = New Bitmap(PictureBox1.Width, PictureBox1.Height) >> Dim g As Graphics = Graphics.FromImage(bit) >> Dim myPen As Pen = New Pen(Color.Red, 1) >> c = 10 >> inc = 20 >> For i = 0 To 30 >> PictureBox1.CreateGraphics.DrawLine(myPen, PictureBox1.Left, c + i * > > Replace 'PictureBox1.CreateGraphics.DrawLine' with 'e.DrawLine'. This > should solve the problem. > > -- > M S Herfried K. Wagner > M V P <URL:http://dotnet.mvps.org/> > V B <URL:http://classicvb.org/petition/> Ed,
"Ed Bitzer" <edbit***@yahoo.com> schrieb: Feel free to ask if you have any further questions.> And it does as advertised. I just to have to get a third book to learn my > fundamentals so that I can use the help system which truly is extensive - > you just have to have the fundamentals down first. > Glad I don't do this for a living<g>. ;-)-- M S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://classicvb.org/petition/> See the GDI+ FAQ for explanations of why CreateGraphics is a bad idea.
-- Show quoteHide quoteBob Powell [MVP] Visual C#, System.Drawing 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. "Ed Bitzer" <edbit***@yahoo.com> wrote in message news:O0XzXpEOFHA.3296@TK2MSFTNGP15.phx.gbl... > Can draw a line on my form with a button click event but cannot upon the > Load event when I wish. No more line object so used the following: > Dim bit As Bitmap = New Bitmap(Me.Width, Me.Height) > Dim g As Graphics = Graphics.FromImage(bit) > Dim myPen As Pen = New Pen(Color.Blue, 1) > Me.CreateGraphics.DrawLine(myPen, 0, 5, Me.Width, 5) > Appreciate some help. > > Ed > Here's an MSDN sample of how to create Line Controls:
http://download.microsoft.com/download/7/e/0/7e070297-47fe-4443-9194-ab57acd8ea01/LineControls.msi Bob, I've seen a lot of posts saying CreateGraphics is a bad Idea, mostly
they say because of encapuslation and it doesn't work with double buffering. I've yet to really understand why it is a bad to use it so long as one doesn't use double buffering...is there some fear that this won't work in future releases of VB.Net and if so, why aren't we worried about several other things the probably will change in future releases? Why the CreateGraphics worry..do you have some insight as to what Microsoft will do? Show quoteHide quote "Bob Powell [MVP]" wrote: > See the GDI+ FAQ for explanations of why CreateGraphics is a bad idea. > > -- > Bob Powell [MVP] > Visual C#, System.Drawing > > 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. > > > > > > "Ed Bitzer" <edbit***@yahoo.com> wrote in message > news:O0XzXpEOFHA.3296@TK2MSFTNGP15.phx.gbl... > > Can draw a line on my form with a button click event but cannot upon the > > Load event when I wish. No more line object so used the following: > > Dim bit As Bitmap = New Bitmap(Me.Width, Me.Height) > > Dim g As Graphics = Graphics.FromImage(bit) > > Dim myPen As Pen = New Pen(Color.Blue, 1) > > Me.CreateGraphics.DrawLine(myPen, 0, 5, Me.Width, 5) > > Appreciate some help. > > > > Ed > > > > > The problem with using the CreateGraphics call for any purpose other than
obtaining data about the Graphics object of a particular window is that it breaks the fundamental principle of event driven programming. Windows is an event driven system in which things happen in order and for a purpose. When you write code that refuses to follow the order of events as dictated by the system you will have your own misguided efforts walked upon by the *correct functioning* of the system. Painting using CreateGraphics will almost inevitably be overprinted by the OnPaint method and causes huge numbers of questions from inexperienced programmers who think that there is some sort of system error when it's their own code that's at fault. This is why it's still the GDI+ FAQ most asked question despite three years of the answer being available for all to see with a simple google search. It's also why I generally answer such questions with a brusque "RTFM" style answer so, after you've "Read That Fine Material" ;-) you'll understand fully. Microsoft's operating systems, including Longhorn, will continue to be event driven and will exhibit the same behaviours if event order is ignored whether it's GDI, GDI+ or Avalon doing the drawing. -- Show quoteHide quoteBob Powell [MVP] Visual C#, System.Drawing 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. "Dennis" <Den***@discussions.microsoft.com> wrote in message news:75502B37-55A1-44C0-ACF3-4A27BDC7004E@microsoft.com... > Bob, I've seen a lot of posts saying CreateGraphics is a bad Idea, mostly > they say because of encapuslation and it doesn't work with double > buffering. > I've yet to really understand why it is a bad to use it so long as one > doesn't use double buffering...is there some fear that this won't work in > future releases of VB.Net and if so, why aren't we worried about several > other things the probably will change in future releases? Why the > CreateGraphics worry..do you have some insight as to what Microsoft will > do? > > "Bob Powell [MVP]" wrote: > >> See the GDI+ FAQ for explanations of why CreateGraphics is a bad idea. >> >> -- >> Bob Powell [MVP] >> Visual C#, System.Drawing >> >> 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. >> >> >> >> >> >> "Ed Bitzer" <edbit***@yahoo.com> wrote in message >> news:O0XzXpEOFHA.3296@TK2MSFTNGP15.phx.gbl... >> > Can draw a line on my form with a button click event but cannot upon >> > the >> > Load event when I wish. No more line object so used the following: >> > Dim bit As Bitmap = New Bitmap(Me.Width, Me.Height) >> > Dim g As Graphics = Graphics.FromImage(bit) >> > Dim myPen As Pen = New Pen(Color.Blue, 1) >> > Me.CreateGraphics.DrawLine(myPen, 0, 5, Me.Width, 5) >> > Appreciate some help. >> > >> > Ed >> > >> >> >> Thanks for your time in answering my question. I use the graphics object
passed by the "OnPaint" event for the most part but I do have one usercontrol that creates a graphics object for the control when it's first instantiated then re-creates the graphics object each time the control is moved or resized...this seems to work OK as I've used it a lot. I do plan, however, to convert it to drawing on a bitmap then BltBit copying the parts that need refreshed in the OnPaint event when I get time. Show quoteHide quote "Bob Powell [MVP]" wrote: > The problem with using the CreateGraphics call for any purpose other than > obtaining data about the Graphics object of a particular window is that it > breaks the fundamental principle of event driven programming. > > Windows is an event driven system in which things happen in order and for a > purpose. When you write code that refuses to follow the order of events as > dictated by the system you will have your own misguided efforts walked upon > by the *correct functioning* of the system. > > Painting using CreateGraphics will almost inevitably be overprinted by the > OnPaint method and causes huge numbers of questions from inexperienced > programmers who think that there is some sort of system error when it's > their own code that's at fault. This is why it's still the GDI+ FAQ most > asked question despite three years of the answer being available for all to > see with a simple google search. > > It's also why I generally answer such questions with a brusque "RTFM" style > answer so, after you've "Read That Fine Material" ;-) you'll understand > fully. > > Microsoft's operating systems, including Longhorn, will continue to be event > driven and will exhibit the same behaviours if event order is ignored > whether it's GDI, GDI+ or Avalon doing the drawing. > > -- > Bob Powell [MVP] > Visual C#, System.Drawing > > 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. > > > > > > "Dennis" <Den***@discussions.microsoft.com> wrote in message > news:75502B37-55A1-44C0-ACF3-4A27BDC7004E@microsoft.com... > > Bob, I've seen a lot of posts saying CreateGraphics is a bad Idea, mostly > > they say because of encapuslation and it doesn't work with double > > buffering. > > I've yet to really understand why it is a bad to use it so long as one > > doesn't use double buffering...is there some fear that this won't work in > > future releases of VB.Net and if so, why aren't we worried about several > > other things the probably will change in future releases? Why the > > CreateGraphics worry..do you have some insight as to what Microsoft will > > do? > > > > "Bob Powell [MVP]" wrote: > > > >> See the GDI+ FAQ for explanations of why CreateGraphics is a bad idea. > >> > >> -- > >> Bob Powell [MVP] > >> Visual C#, System.Drawing > >> > >> 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. > >> > >> > >> > >> > >> > >> "Ed Bitzer" <edbit***@yahoo.com> wrote in message > >> news:O0XzXpEOFHA.3296@TK2MSFTNGP15.phx.gbl... > >> > Can draw a line on my form with a button click event but cannot upon > >> > the > >> > Load event when I wish. No more line object so used the following: > >> > Dim bit As Bitmap = New Bitmap(Me.Width, Me.Height) > >> > Dim g As Graphics = Graphics.FromImage(bit) > >> > Dim myPen As Pen = New Pen(Color.Blue, 1) > >> > Me.CreateGraphics.DrawLine(myPen, 0, 5, Me.Width, 5) > >> > Appreciate some help. > >> > > >> > Ed > >> > > >> > >> > >> > > > Bob Powell [MVP] wrote:
(snip) > Microsoft's operating systems, including Longhorn, will continue to "GDI+ no longer supported in LongHorn" - Bob Powell!be event > driven and will exhibit the same behaviours if event order is ignored > whether it's GDI, GDI+ or Avalon doing the drawing. TC Then what you are saying is that Longhorn will not support the CreateGraphics
method...is this correct? If so, then what other things won't be backward compataible with VB.Net? Show quoteHide quote "aatcbbtcc***@yahoo.com" wrote: > > Bob Powell [MVP] wrote: > > (snip) > > > Microsoft's operating systems, including Longhorn, will continue to > be event > > driven and will exhibit the same behaviours if event order is ignored > > > whether it's GDI, GDI+ or Avalon doing the drawing. > > > "GDI+ no longer supported in LongHorn" - Bob Powell! > > TC > > Hi Dennis
Sorry, I only just saw your reply. On April 1, Bob Powell [MVP] posted to microsoft.public.dotnet.framework, subject: "GDI+ no longer supported in LongHorn", saying that GDI+ would not be supported in LongHorn. I thought that this was probably an April Fool's joke. However, I do not work in the .NET environment yet, and I have recently been suffering some major grief in regard to Microsoft's "start again" move from VB[A] to VB.NET. So his post did not seem obviously unreasonable, given Microsoft's blunt abandonment of older applications comprising millions of lines of VB[A] code. Most of that code will have to be rewritten from scratch. This will put many one-man shops, like me, out of business. I asked him to confirm that his post was a joke, but he did not reply. That was very stupid, in my opinion, unless it was actually true. But I *think* that it was a joke, because no-one else has objected, so far. Cheers, TC And why should I care about GDI+? Because I have spent the past 6
months integrating the redistributable gdiplus.dll into my 75,000 line VBA applicaton :-(( TC 
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