Develop Reference

Draw horizontal line in ListView to show dropping place

When in Foobar2000 I drag-and-drop files into playlist, the ListView shows the place of dropping tracks:
I'm looking for a way to implement this feature. Is it just drawn by Graphics library, or do I have some implemented method to show horizontal line on ListView?

At least with a ListView control, there is some limited built-in support provided by way of the InsertionMark property, but this only works in icon view, small icon view, and tile view. It doesn't work when the Items are sorted or when groups are turned on, and it requires comctrl32.dll version 6 (thus meaning Windows XP or later, with Visual Styles enabled).
If you want a more general solution, you can easily draw a line yourself in the DragOver event:
To avoid flicker we remember the last index:
int prevItem = -1;
The event uses a HitTest to determine the item under the cursor..:
private void listView1_DragOver(object sender, DragEventArgs e)
{
Point mLoc = listView1.PointToClient(Cursor.Position);
var hitt = listView1.HitTest(mLoc);
if (hitt.Item == null) return;
int idx = hitt.Item.Index;
if (idx == prevItem) return;
listView2.Refresh();
using (Graphics g = listView1.CreateGraphics())
{
Rectangle rect = listView1.GetItemRect(idx);
g.DrawLine(Pens.Red, rect.Left, rect.Top, rect.Right, rect.Top);
}
prevItem = idx;
}
If you want to use a ListBox, the code is pretty much the same:
private void listBox1_DragOver(object sender, DragEventArgs e)
{
Point mLoc = listBox1.PointToClient(Cursor.Position);
int idx = listBox1.IndexFromPoint(mLoc);
if (idx < 0) return;
if (idx == prevItem) return;
listBox1.Refresh();
using (Graphics g = listBox1.CreateGraphics())
{
Rectangle rect = listBox1.GetItemRectangle(idx);
g.DrawLine(Pens.Red, rect.Left, rect.Top, rect.Right, rect.Top);
}
prevItem = idx;
}
Also do a Refresh to clear the line in the DragLeave event and also in the DragDrop event!
Note the this is one of the rare situations when you want to use control.CreateGraphics because the drawing is meant to be non-persistent! Normally all graphics should be drawn with the e.Graphics object in the Paint event!

how to avoid blank area treeview node clicking?

I am working on a regular WinForm Outlook Addin and I have created a Treeview using DrawNode event, The tree is working as expected but there is a glitch in node clicking, only the green region is clickable and the half node gets non responsive.
When I use the MouseDown event the whole area gets clickable including the blank space right next to the node. But to restrict this blank clicking I am using a logic with the help of TreeViewHitTestLocations I am checking if the clicked location is the RightOfLabel then don't do anything but unfortunately this doesn't give me a precise result, it somehow gets confuse and takes right half of the label(Node) as the blank space and doesn't get clicked.
Note: I think this all happened because I played with DrawNode method and while keeping the distance between label and workspace icon the application underneath assumes that the label gets finish within the green portion so the red portion gets left as a blank space. This is just my assumption based on all the naïve things I have done with the method.
Need help to resolve this issue if someone can guide me to a fix. Thanks
void treeview_mousedown(object sender, MouseEventArgs e)
{
TreeNode nodeClicked;
// if arrow up/down will be excluded from the mousedown event
var hitTest = this.HitTest(e.Location);
if (hitTest.Location == TreeViewHitTestLocations.PlusMinus)
return;
if (hitTest.Location == TreeViewHitTestLocations.RightOfLabel)
return;
// Get the node clicked on
nodeClicked = this.GetNodeAt(e.X, e.Y);
// Was the node clicked on?
if (!(nodeClicked == null))
this.SelectedNode = nodeClicked;
}
Below is the treeview drawnode method I am using:
void treeview_DrawNode(object sender, DrawTreeNodeEventArgs e)
{
Rectangle nodeRect = e.Node.Bounds;
// below location is the expand and collapse icon location
Point ptExpand = new Point(nodeRect.Location.X - 7, nodeRect.Location.Y + 5);
Image expandImg = null;
// check the below condition for nodes with child nodes and nodes without child nodes
if ( e.Node.Nodes.Count < 1)
expandImg = global::myresource.OfficeAddin.Controls.Resource.search;
else if (e.Node.IsExpanded && e.Node.Nodes.Count > 1)
expandImg = global::myresource.OfficeAddin.Controls.Resource.down_arrow_icon;
else
expandImg = global::myresource.OfficeAddin.Controls.Resource.right_arrow_icon;
Graphics g = Graphics.FromImage(expandImg);
IntPtr imgPtr = g.GetHdc();
g.ReleaseHdc();
e.Graphics.DrawImage(expandImg, ptExpand);
// draw node icon
Point ptNodeIcon = new Point(nodeRect.Location.X - 4, nodeRect.Location.Y + 2);
Image nodeImg = global::myresource.OfficeAddin.Controls.Resource.folder_icon_16px;
g = Graphics.FromImage(nodeImg);
imgPtr = g.GetHdc();
g.ReleaseHdc();
e.Graphics.DrawImage(nodeImg, ptNodeIcon);
// draw node text
Font nodeFont = e.Node.NodeFont;
if (e.Node.NodeFont != null)
{
nodeFont = e.Node.NodeFont;
} else {
nodeFont = new System.Drawing.Font("Segoe UI", 10F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
}
// set the forecolor
Color forecolor = e.Node.ForeColor;
// color same as the font color
string strSelectedColor = #"#505050";
Color selectedColor = System.Drawing.ColorTranslator.FromHtml(strSelectedColor);
SolidBrush selectedTreeBrush = new SolidBrush(selectedColor);
//Inflate to not be cut
Rectangle textRect = nodeRect;
//below value controls the width of the text if given less then, long texts will come in multiple lines
textRect.Width += 150;
// below value controls the over all width of the node, if given less all the things will get sqeeze
e.Graphics.DrawString(e.Node.Text, nodeFont, selectedTreeBrush , Rectangle.Inflate(textRect, -20, 0));
}

Your assumption is right, you can check it by marking the bounds at drawing, for example:
TreeNodeStates state = e.State;
bool isFocused = (state & TreeNodeStates.Focused) == TreeNodeStates.Focused;
if (isFocused)
ControlPaint.DrawFocusRectangle(e.Graphics, e.Bounds, foreColor, backColor);
Your code has more problems:
Issue 1: Images
If you use icons for nodes use the TreeView.ImageList and TreeNode.ImageKey properties. Otherwise, no space will be allocated for the image at drawing. In this case you can use TreeViewDrawMode.OwnerDrawText DrawMode.
Issue 2: Fonts
Do not use other font than the font of the node or the tree because it can have unexpected size. If this SegoeUI font is a default one use it at your TreeView instance instead. Then you can obtain the required font like this:
Font font = e.Node.NodeFont ?? e.Node.TreeView.Font;
Issue 3: Texts
You use Graphics.DrawString for drawing texts, which uses GDI+. However, starting with .NET 2.0 the default text rendering method is by GDI, unless CompatibleTextRendering property of a control is true. They produce slightly different text sizes.
To use GDI, for which the size of a label is calculated use the TextRenderer class instead:
TextRenderer.DrawText(e.Graphics, e.Node.Text, font, e.Bounds, foreColor, TextFormatFlags.GlyphOverhangPadding | TextFormatFlags.SingleLine | TextFormatFlags.EndEllipsis | TextFormatFlags.NoPrefix);

Custom ListView control will not paint when first shown

I have created a custom ListView control to suit my needs and I'm having an issue that causes the ListView not to show any contents (not drawing anything, just white) when the form first loads.
If I resize the form or click on my control (anything that forces a repaint on the ListView) then it shows up as expected.
As a side note, it used to work just fine until I made a small change today and rebuilt the control. I removed all the changes I made and rebuilt again but the issue still happens. Any ideas as to why it will not show up (paint) when the form is first loaded?
This is what I use to do the custom drawing on my custom ListView control...
protected override void OnDrawItem(DrawListViewItemEventArgs e)
{
Image image = e.Item.ImageList.Images[e.Item.ImageIndex];
Size textSize = new Size((int)e.Graphics.MeasureString(e.Item.Text, e.Item.Font).Width, (int)e.Graphics.MeasureString(e.Item.Text, e.Item.Font).Height);
//Get the area of the item to be painted
Rectangle bounds = e.Bounds;
bounds.X = 0;
bounds.Width = this.Width;
//Set the spacing on the list view items
int hPadding = 0;
int vPadding = 0;
IntPtr padding = (IntPtr)(int)(((ushort)(hPadding + bounds.Width)) | (uint)((vPadding + bounds.Height) << 16));
SendMessage(this.Handle, (uint)ListViewMessage.LVM_SETICONSPACING, IntPtr.Zero, padding);
//Set the positions of the image and text
int imageLeft = (bounds.Width / 2) - (image.Width / 2);
int imageTop = bounds.Top + 3;
int textLeft = (bounds.Width / 2) - (textSize.Width / 2);
int textTop = imageTop + image.Height;
Point imagePosition = new Point(imageLeft, imageTop);
Point textPosition = new Point(textLeft, textTop);
//Draw background
using (Brush brush = new SolidBrush(e.Item.BackColor))
e.Graphics.FillRectangle(brush, bounds);
//Draw selected
if (e.Item.Selected)
{
using (Brush brush = new SolidBrush(m_SelectedColor))
e.Graphics.FillRectangle(brush, bounds);
}
//Draw image
e.Graphics.DrawImage(image, imagePosition);
//Draw text
e.Graphics.DrawString(e.Item.Text, e.Item.Font, new SolidBrush(e.Item.ForeColor), textPosition);
}
I also set the following things in the Constructor of my custom control...
public MyListView()
{
this.DoubleBuffered = true;
this.OwnerDraw = true;
this.View = View.LargeIcon;
this.Cursor = Cursors.Hand;
this.Scrollable = false;
}
I also inherit the ListView class...
public class MyListView : ListView
{
//All my source
}

You need to set the set the control to redraw itself when resized. So add this code in constructor of your control:
this.ResizeRedraw = true;

My apologies:
Doing the below reset my event handlers and the problem went away. However, once I hooked them up, I found the Resize event handler that I used to set the ColumnWidth was causing the issue. Why setting the ColumnWidth is causing this, I do not know.
Arvo Bowen's comment on this answer fixed it for me also (.NET 4.8 Framework, VS2022). To be clear, not requiring this.ResizeRedraw = true; from the answer.
So after much headache and time I found that I had absolutely nothing wrong with my control. It was your answer that made me create another control just like my existing one and test it. To my surprise it worked great. I simply copied my existing non-working control and pasted it on the form and then new one worked! Sometimes VS just does weird things... Somehow I managed to muck up the control's creation object or something..

Can't get Control.OnPaint method to work

I couldnt find anything like that at all (basicly every problem from so else is always a syntax problem) and well..., the situation is a bit more complicated. to avoid using 500 lines of code im going to describe it for the most part:
Ive got a Form wich is acting as a parent Form (MdiParent) and another Form wich is a Child but basicly a fully functional Form at its own. Im using several OnPaint methods in the childform, witch work perfectly fine, and 3 custom buttons on the parent Form witch also have their own OnPaint methods. These 3 buttons (actualy panels) and every other control on the parent Form are contained in a PictureBox witch fills the parent Form completely and is used to make the background of the parent transparent / clickthrough via TransparencyKey (havnt found any other ways of doing that).
the Problem is that every OnPaint Method on the parent wont work at all (they're beeing executed but dont paint anything).
here is some code but that isnt the problem i'd say:
this.myButtonObject1.BackColor = System.Drawing.Color.Red;
this.myButtonObject1.Location = new System.Drawing.Point(840, 0);
this.myButtonObject1.Name = "myButtonObject1";
this.myButtonObject1.Size = new System.Drawing.Size(50, 50);
this.myButtonObject1.TabIndex = 0;
this.myButtonObject1.Click += new System.EventHandler(this.myButton1_Click);
this.myButtonObject1.Paint += new System.Windows.Forms.PaintEventHandler(this.myButtonObject1_Paint);
private void myButtonObject1_Paint(object sender, PaintEventArgs e)
{
Graphics g = e.Graphics;
LinearGradientBrush lgb = new LinearGradientBrush(new PointF(0, 0), new PointF(myButtonObject1.Width, myButtonObject1.Height), Color.Green, Color.Lime);
Pen p = new Pen(lgb, 5);
g.DrawRectangle(p, myButtonObject1.Bounds);
lgb.Dispose();
p.Dispose();
}
if anyone can tell me; what am i doing wrong?
PS: i m using .net 4.5, VS 2015, and havnt changed any of the default settings besides TopMost FormBorderStyle ShowInTaskbar StartPosition and ofc the color and trancparencyKey, but i dont think it has anything todo with that.

Update
The small error in your code is to use the Panel's Bounds property, which at runtime will refer to the Panel's Location within its Parent! But the drawing code must be relative to the object, not its parent!
So do not use Bounds but ClientRectangle and make sure to set the right PenAlignment:
using (LinearGradientBrush lgb =
new LinearGradientBrush(ClientRectangle, Color.Green, Color.Lime, 0f) ) //or some angle!
using (Pen p = new Pen(lgb, 5))
{
p.Alignment = PenAlignment.Inset;
g.DrawRectangle(p, ClientRectangle);
}

Set myButtonObject1.FlatStyle to FlatStyle.Standard.

Drawn rectangle appears only on last instance of my userControl

I have a userControl which has some programmatically drawn rectangles. I need few instances of that userControl on my form (see the image). The problem is that only the last instance will show the drawn shapes!
I guess it has something to do with drawing surface or the Paint event handler
In case it might help, here's some of the code I use in my control:
private void MyUserControl_Paint(object sender, PaintEventArgs e)
{
showHoraireMaitresse();
Rectangle rec = showDisponibilités();
var b = new SolidBrush(Color.FromArgb(150, Color.Blue));
e.Graphics.FillRectangle (b, rec);
showOccupation();
}
private void showHoraireMaitresse()
{
heureDebut = 8;
for (int i = 0; i < 14; i++)
{
//Label d'heure -> This shows just fine
addLabel(i, heureDebut);
//Rectangles d'heure -> This shows only in last instance
var rectangle = new Rectangle(180 + i * largeurDUneHeure, 14, largeurDUneHeure, 30);
surface.DrawRectangle(defaultPen, rectangle);
}
addLabel(14, heureDebut);
}
Thank you!

Without further information, I'm going to guess that 'surface' is static.
Trace through OnPaint and check which control is painting, and what the bounds are for 'surface'. Perhaps all the controls are painting the same exact rectangle.