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Hi,
I am plotting a graph between frequency on x-axis and gain on y-axis.
X-axis(frequency) needs to vary logarithmically and y-axis(gain) needs to vary linearly.
The first step was to create the axis and put numbers on the lines.
As the default origin is at the Left Top corner of the client area, I moved the origin to the center of the client area and inverted the y-axis, so that whatever drawing takes place it should be as per the new origin and looks more realistic.
I tried to create few lines along with string to number them. Lines are drawn properly, however the string also got inverted.
Here is the code, I tried to use. It can be used in any winform application.
private void Form1_Paint(object sender, PaintEventArgs e)
{
Graphics g = e.Graphics;
g.TranslateTransform(this.ClientSize.Width / 2, this.ClientSize.Height / 2);
g.ScaleTransform(1, -1);
Point A = new Point(0, 0);
Point B = new Point(120, 80);
Point C = new Point(120, -80);
g.DrawLine(Pens.Red, A, B);
g.DrawLine(Pens.Green, A, C);
g.DrawLine(Pens.Purple, 0, 0, -50, 70);
g.DrawString("3", new Font("Arial", 16), new SolidBrush(Color.Purple), B);
}
Question 1: How can we draw string after inverting the y-axis?
Question 2: How can we make vertical lines that should vary logarithmically?
Any idea/solution is welcome.
Praveen Raghuvanshi
Software Developer
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Leave the graphics object untranslated and untransformed. Do the y-axis inversion and scaling in separate code instead. That way, you have full control over what is drawn where.
A good idea would be to encapsulate all of that conversion processing so that you can call it using just "normal" values.
Ciao,
luker
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Thanks Lukeer!!!
I tried your suggestion, missed somewhere.
Appreciate if you can help me draw three lines with numbering on them according to the order of drawing them.
I wish to have origin in the center of the window and all points should be given according to that. Y-axis should be positive in the upward direction and negative in the downward direction.
Thanks,
Praveen Raghuvanshi
Software Developer
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Here is a quick proposal with horrible readablility:
private PointF Transform(PointF logicalPoint)
{
float logicalXMin = -100;
float logicalXMax = 100;
float logicalYMin = -100;
float logicalYMax = 100;
float canvasXMin = this.ClientRectangle.Left;
float canvasXMax = this.ClientRectangle.Right;
float canvasYMin = this.ClientRectangle.Top;
float canvasYMax = this.ClientRectangle.Bottom;
float canvasX = ((((float)(Math.Log(logicalPoint.X, 10))) - logicalXMin) / (logicalXMax - logicalXMin) * (canvasXMax - canvasXMin)) + canvasXMin;
float canvasY = ((-logicalPoint.Y - logicalYMin ) / (logicalYMax - logicalYMin) * (canvasYMax - canvasYMin)) + canvasYMin;
return (new PointF(canvasX, canvasY));
}
You use a control as canvas. You have to transform logical co-ordinates into canvas co-ordinates. Therefore you look at your logical value in relation to logical maximum and minimum. Then apply the same relation to canvas minimum and maximum.
Since canvas Y-axis is inverted, you have to use negative logical Y value to compensate.
As mathematics dictates, you can't use negative X values here.
Draw grid lines using logical co-ordinates. They should get processed just as any data point.
for( int power = 0, power < 4, power++)
{
g.DrawLine( gridPen, Math.Pow(1, power), logicalYMin, Math.Pow(1, power), logicalYMax);
g.DrawLine( gridPen, Math.Pow(2, power), logicalYMin, Math.Pow(2, power), logicalYMax);
g.DrawLine( gridPen, Math.Pow(5, power), logicalYMin, Math.Pow(5, power), logicalYMax);
}Horizontal grid lines should be even easier.
for( int i = logicalYMin; i <= logicalYMax; i += 10)
{
g.DrawLine( gridPen, logicalXMin, i, logicalXMax, i);
}
Ciao,
luker
modified on Wednesday, July 13, 2011 7:17 AM
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Thanks, I will give a shot.
Praveen Raghuvanshi
Software Developer
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As Lukeer says, you should calculate the canvas position from chart coordinates yourself. Using translate and scale seems clever but as you've discovered it causes text to be drawn upside down as well.
When I draw a log chart I still place gridlines linearly but label them logarithmically (e.g. 0.5, 1, 2, 4, or 1, 10, 100, 1000). I find the 'log graphpaper' approach to be fussy and generally not helpful. But if you want to do that then it is easy enough to calculate the appropriate chart coordinate Y values (log y at sensible Y values such as 1, 2, 5 each power of 10), and then you can transform those like all the other things for drawing.
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XMLTextReader has a depth property that returns the depth of the current node. Anyone know a way to determine the maximum depth? I guess I could read through the file first, but that doesn't seem very efficient.
Everything makes sense in someone's mind
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Until you read through the file, the XML reader wouldn't know anyway (even if, as another example, you used an XPathNavigator to search only leaf nodes). But a better question is why you need to find depth? Because to do so may be considered inefficient, maybe first you should determine if you really need to.
This posting is provided "AS IS" with no warranties, and confers no rights.
Program Manager
Visual Studio Professional Deployment Experience
Microsoft
[My Articles] [My Blog] [Follow on Twitter]
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XML doesn't include structure metadata in a header or anything, so to find the maximum depth you would have to read the whole document and check every node.
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I googled and found none... according to MSDN, in framework 4, there is vertical alighment property available (see [RichTextBox Property]). Not sure how I can get that implemented.
Pls 'F1'!
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Hello Blubbo,
property of vertical alignment of text on RichTextBox control is not available,
Bye
Carmelo La Monica
modified on Tuesday, July 12, 2011 3:06 PM
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Oh, the link I provided was for the cellphone (something like that).... so is there a such way to do that anyway?
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Hello blubb,
the link you posted refers to if you use WPF, what technology you're using?
Bye
Carmelo La Monica
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Visual Studio c# for windows (not WPF)
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Okay, so I'm thinking my problem here probably involves completely misunderstanding the use of a DataGridView, but here goes:
I'm currently working on learning how to use SQL with C#/.NET using VS2010. I created a DataGridView that's linked to my data table. Adding rows to the DataGridView while the program was running did not actually save the changes to the database, so I created a separate piece using SqlConnection & SqlCommand. This successfully added the rows to the database, but did not update the DataGridView.
So I suppose there are two questions here: How do I save the changes to a DataGridView to the bound data table? and How do I have the DataGridView reload table data?
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While this most definitely doesn't answer your question, here goes:
Don't use DataGridViews to enter/introduce/edit data. Use dedicated windows/forms.
You're life gets a whole lot easier.
The reasons are plenty: more control(like data validation), easier to debug, the app looks nicer...
I only use DataGridViews for displaying data(if that).
All the best,
Dan
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Good to know. Given that I'm at this point just trying to figure out how to use SQL in C#, it's good to know which pieces to avoid. So yes, that answer was useful, even if it didn't actually answer my specific question.
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The updating is usually handled by a DataAdapter.Update -- but as has been said, you won't have a very impressive app.
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I have been struggling HARD to find a solution to this. In order to get some long-term platform compatibility (PC simulator, embedded target, etc.) I am implementing my main code in C, and a GUI emulator in C# as a DLL.
I am able to make calls into the C# DLL from my native code by exposing the DLL functions as COM objects (I think...). Data are passed in and out of the library functions just fine.
I would like to have callbacks made back to the native code when events are triggered in the C# code. You can imagine that when a button is clicked on my fancy C# GUI, my native code gets called. I cannot seem to get this callback mechanism working.
Can anyone please give an example, syntax, etc. for assigning a native callback to a managed C# event (or something like that)?
There are TONS of examples of using managed code to call un-managed DLLs, but very little going to the other way.
Thanks in advance.
-Stuart
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Stuart, you need to expose your event as described in this[^] example. This creates the COM hookup for the event handler that you can reference through your C code.
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Nice one - I think that is going to come in handy to me some day too.
Continuous effort - not strength or intelligence - is the key to unlocking our potential.(Winston Churchill)
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Peter, this is helpful, but at least half of the challenge is on the native (un-managed) side. I think now I have a syntactic problem with registering my native C function with the managed event.
Any more tips?
Thanks!
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That side is going to require you to hook up to the COM event in your C code. You might want to read this[^] article to see how C++ handles it (it should be easy enough to apply this to C).
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"Calling" the managed functions isn't really a problem anymore. The real problem is passing in a reference to the unamanged event handler function into the managed event. Sorry to keep pushing on this, but does sound like you know what you're doing!
Thanks again.
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Have you assigned the IConnectionPoint interface[^]? As you've implemented the event interface in your C#, the CLR Interop automatically applies the juice that hooks this together.
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