Develop Reference

ListBox draw size does not change with change to larger font size

When I increase the font size in my ListBox, the larger text strings get vertically clipped because the item draw rectangle size (spacing) does not increase with the font size. Each lower line of text overlays the previous line of text so that only the tops of letters show in larger font sizes.
Everything works fine with DrawMode.OwnerDrawFixed if I don't change the font sizes. Smaller-than-normal fonts display properly. It's only the larger fonts that get clipped. I changed to DrawMode.OwnerDrawVariable and added a MeasureItem event handler to measure the larger font size explicitly, but that did not work either.
What am I missing? Thank you.
UPDATE: I provided working code below based on #Jimi's examples in the links he provided in his comments. I was missing the idea that the MeasureItem event runs only once (or when necessary) and not for each drawn item. Thus, you must manually trigger a new MeasureItem event when you change the font size in the ListBox. The trick to generating the event is to flip the DrawMode.OwnerDrawVariable to Normal and back.
listBox1.DrawMode = DrawMode.OwnerDrawVariable;
listBox1.DrawItem += DrawItemHandler;
listBox1.MeasureItem += MeasureItemHandler;
private void MeasureItemHandler(object sender, MeasureItemEventArgs e) {
// must measure the height to allow for user font size changes
var listBox = (ListBox) sender;
e.ItemHeight = listBox.Font.Height;
}
public void DrawItemHandler(object sender, DrawItemEventArgs e) {
// prepare text and colors for drawing here
//
using (var bgbrush = new SolidBrush(bgcolor)) {
using (var fgbrush = new SolidBrush(fgcolor)) {
e.Graphics.FillRectangle(bgbrush, e.Bounds);
e.Graphics.DrawString(logEntry.EntryText, e.Font, fgbrush, e.Bounds);
}
}
e.DrawFocusRectangle();
}
private void fontUpToolStripMenuItem_Click(object sender, EventArgs e) {
// To increase size alone, use the original font family
var size = listBox1.Font.Size;
if (size < 32) {
// set the new font size, register it with the list box, and then
// flip the draw mode back and forth to trigger a MeasureItem event.
// The measure event will recalculate the bounds for all items in the box.
listBox1.Font = new Font(listBox1.Font.FontFamily, size + 1);
listBox1.Height = listBox1.Font.Height;
listBox1.DrawMode = DrawMode.Normal;
listBox1.DrawMode = DrawMode.OwnerDrawVariable;
listBox1.Invalidate();
}
}

C# Label highlight and remove highlight

I'm sure this is something very easy to figure out but I cannot do it. I have a winform with 3 Label inside a Panel. When the form loads, the first Label has a Paint event that draws a rectangle on it. I would like a backgroundWorker to go through each one, wait 5 seconds, restore the Label to normal (redrawing I'm guessing) and then draw a rectangle on the following Label.
public List<Label> GetLabelList()
{
return new List<List>()
{
label1,
label2,
label3,
label4
};
}
private void bgBackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
var getList = GetLabelList();
for (int i = 0; i < getList.Count; i++)
{
if ((bgBackgroundWorker.CancellationPending == true))
{
e.Cancel = true;
break;
}
else
{
Thread.Sleep(5000);
getList [i].Paint += RemoveLabelHighlight;
getList [i].Invalidate();
if (i < 2)
{
getList [i + 1].Paint += AddLabelHighlight;
getList [i + 1].Invalidate();
}
bgBackgroundWorker.ReportProgress((i * 10));
}
}
}
private void AddLabelHighlight(object sender, PaintEventArgs e)
{
var label = sender as Label;
e.Graphics.DrawRectangle(new Pen(Color.DeepPink, 8), label.ClientRectangle);
}
private void RemoveLabelHighlight(object sender, PaintEventArgs e)
{
var label = sender as Label;
e.Graphics.DrawRectangle(new Pen(Color.Green, 8), label.ClientRectangle); // This should return the Label back to original state
}
This works but when the rectangle is drawn, the label is cut off all the way around. Any suggestions?
Also, I'm sure there is a much better and more efficient way to achieve this, maybe by an EventHandler or something. I'd like some suggestions, if possible.

This is actually being caused by your use of the pen width of 8 pixels, I believe. Try a different size and see if that changes the size of the rectangle not being drawn.
To fill the rectangle instead, use:
e.Graphics.FillRectangle(new SolidBrush(Color.DeepPink), e.ClipRectangle);
EDIT Since you're now completely responsible for drawing the control, the text can be redrawn with a DrawString call:
e.Graphics.DrawString(label.Text, label.Font, SystemBrushes.ControlText, new PointF(0,0));
EDIT Here's how to nest a panel and a label to achieve what you're looking for:
Add a new panel, set the padding to 8,8,8,8, and BackColor to whatever you like
Add a new label to this panel, set it's AutoSize property to false, Dock property to Fill, and TextAlign property to MiddleCenter
While I have always loved doing owner-drawn stuff, sometimes it's just easier to use what's there! For fun though, I would wrap this into a new Panel-derived control to make it easy to reuse.

How to make group box text alignment center in win forms?

I am using a group box and there are several controls inside this.
My requirement is to set the group box title to the middle of the group box instead of Left.
How?

you can extend the group box class like this.
public class CustomGrpBox : GroupBox
{
private string _Text = "";
public CustomGrpBox()
{
//set the base text to empty
//base class will draw empty string
//in such way we see only text what we draw
base.Text = "";
}
//create a new property a
[Browsable(true)]
[Category("Appearance")]
[DefaultValue("GroupBoxText")]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Visible)]
public new string Text
{
get
{
return _Text;
}
set
{
_Text = value;
this.Invalidate();
}
}
protected override void OnPaint(PaintEventArgs e)
{
//first let the base class to draw the control
base.OnPaint(e);
//create a brush with fore color
SolidBrush colorBrush = new SolidBrush(this.ForeColor);
//create a brush with back color
var backColor = new SolidBrush(this.BackColor);
//measure the text size
var size = TextRenderer.MeasureText(this.Text, this.Font);
// evaluate the postiong of text from left;
int left = (this.Width - size.Width) / 2;
//draw a fill rectangle in order to remove the border
e.Graphics.FillRectangle(backColor, new Rectangle(left, 0, size.Width, size.Height));
//draw the text Now
e.Graphics.DrawString(this.Text, this.Font, colorBrush, new PointF(left, 0));
}
}
add the above class into your project and use "CustomGrpBox" instead of "GroupBox" which will be created after build in your tool box.
and you can set the text any time like this.
private void Form2_Load(object sender, EventArgs e)
{
customGrpBox1.Text = "Hello World";
}
it will look like this in design time visual studio

Unfortunately, you may set the title on the right by using the RightToLeft property, but there is no property to set it in the middle.
What you can do is to set an empty Text in your GroupBox, create a Label with the title and put that label above the GroupBox (with the same parent).
You may do it dynamically at form initialization by calling following procedure:
private void CenterGroupBoxTitle(GroupBox groupbox)
{
Label label = new Label() ;
label.Text = groupbox.Text ;
groupbox.Text = "" ;
label.Left = groupbox.Left+(groupbox.Width-label.Width)/2 ;
label.Top = groupbox.Top + 2 ; // 2 is an example : adjust the constant
label.Parent = groupbox.Parent ;
label.BringToFront() ;
}

Try to create a custom control using Panel as container and draw border around this, you can then have full control of the title's alignment.
If you would like a simple approach, you can leave the groupbox's title as empty text, and then place a label at the center position of the groupbox. You can also define this as user-control so you wouldn't need to do this repeatedly.

Not an eloquent solution, but if you have a simple GroupBox, that stays the( same size, you can just pad the beginning, and the end with spaces.
example : GroupBox.Text = " This is the groupbox text ";
The amount of padding of space's will depend on the length of the box.
Of course you'll lose some of the GroupBox's beginning and end lines on top, and if that's important, then Answer 3 seems like a good solution.

OwnerDraw DrawItem event on my combobox also changes the Text property value

My question is basically, does implementing DrawItem for my ComboBox in WinForms, change my Text property, why and I can I stop it?
Because my OwnerDraw event works perfectly except the Text property "also" gets set to the same logic as all the items in Items[] (ie implemented in DrawItem event below)
For context, I show URL's in the list, but some are so long I basically chop them and put the text "..." at the end - to make it more readable. I have DataSource set so that it renders one property of my class "DisplayUrl" but uses another "Url" for the actual value. (MyUrl below)
At the end of some code, I explicitly set cmbUrl.Text = "THE FULL TEXT"
But somehow the DrawItem event is also effecting the "Text" property because even after running this code, once the DrawItem event is finished my Text property is set to the same as Item[0]. ie With the text chopped off - as in "THE FULL T..."
void cmbUrl_DrawItem(object sender, DrawItemEventArgs e)
{
var text = ((MyUrl)((ComboBox)sender).Items[e.Index]).DisplayUrl;
var brush = text.Contains("bla) ? Brushes.DarkGreen : Brushes.Black;
// Fill in the background
e.Graphics.FillRectangle(new SolidBrush(e.BackColor), e.Bounds);
if (e.Index < 0) return;
// Work out where every thing goes
int nX = e.Bounds.Left;
int nY = e.Bounds.Top;
const int nMarg = 2;
int nH = e.Bounds.Height - (2 * nMarg);
// Draw the Colour Gymph
var penFore = new Pen(e.ForeColor);
var rectGymph = new Rectangle(nX + nMarg, nY + nMarg, nH, nH);
e.Graphics.FillRectangle(brush, rectGymph);
e.Graphics.DrawRectangle(penFore, rectGymph);
var fullWidth = nX + nH + (2 * nMarg);
e.Graphics.DrawString(text, e.Font, brush, fullWidth, e.Bounds.Top);
}

I think you want to show your the full Text in your combobox and just want to show the short text in Items drop-down list, so the solution may be this:
private void cmbUrl_DropDown(object sender, EventArgs e){
cmbUrl.DisplayMember = "DisplayUrl";
}
private void cmbUrl_DropDownClosed(object sender, EventArgs e){
cmbUrl.DisplayMember = "Url";
}

Temperature TextBox In C#

I need some code to convert standard C# TextBox to temperature TextBox which means adding "°C" to end of the text in the textbox with another color than the default color.

To get the degree symbol you can use character code 176 e.g.
Char degree = (Char)176
You can then append this to your textbox content or I would just add a label to the right of the textbox with the degree symbol if you want to control the forecolor easily.

TextBox is a plain text editor. To get different colours you would have to muck around with a rich text box. Why not put the "°C" in a label positioned to the right of the text box? That would also make your parsing and rendering code much easier.

You could probably create your own control which inherits from TextBox and then override Text property to automaticaly add °C though other color inside the same TextBox could be problem.
Why you want to have °C in TextBox ?
Can't it just be label right after TextBox ?
You can set static text and color to what you want.

The other solutions proposed here are probably sufficient for your application; however, if you had the need to implement this with re-usability in mind, here is a custom control solution which you may extend to better suit your application:
public class TemperatureTextBox : ContainerControl
{
private const int BORDER_SIZE = 1;
// Exposes text property of text box,
// expose other text box properties as needed:
public override string Text
{
get { return textBox.Text; }
set { textBox.Text = value; }
}
private TextBox textBox = new TextBox()
{
Text = string.Empty,
BorderStyle = BorderStyle.None,
Dock = DockStyle.Fill
};
private Label label = new Label()
{
Text = "°C",
TextAlign = ContentAlignment.MiddleCenter,
Size = new Size()
{
Width = 32
},
BackColor = SystemColors.Window,
Dock = DockStyle.Right
};
public TemperatureTextBox()
{
this.BackColor = SystemColors.Window;
this.Padding = new Padding(BORDER_SIZE);
this.Controls.Add(label);
this.Controls.Add(textBox);
this.PerformLayout();
}
// Constrain control size to textbox height plus top and bottom border:
protected override void OnResize(EventArgs e)
{
base.OnResize(e);
this.Height = (textBox.Height + (BORDER_SIZE * 2));
}
// Render a border around the control:
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
e.Graphics.DrawRectangle(
SystemPens.ControlDarkDark,
new Rectangle()
{
Width = (this.Width - BORDER_SIZE),
Height = (this.Height - BORDER_SIZE)
});
}
}
Simply create a new class and drop this code in and rebuild you solution. It will create a new TemperatureTextBox control in the toolbox which can be dropped onto a new form and visually designed.
This example exposes the Text property of the underlying text box by overriding the custom control's text property. You may want to expose other properties, and events depending on what your application needs to accomplish.