Similar to Visual Studio's form designer, be able to identify and snap a shape as it's being dragged to other shape centers and edges.
Ability to snap to grid spacing.

Implement zoom.

Particularly an interesting problem when a shape is completely underneath another shape, and the cursor's selection point could select both. How do we show the completely hidden shape as selected?

Create a selection box that only partially includes a shape. Note that the partially included shape is part of the selected shapes. This is particularly annoying when grouping shapes with connectors that you don't want as part of the group.

Implement shape rotation.

I was drawing the diagram you can see on this screenshot:

The vertical lines are impossible to place after adding the text boxes ("Target", "Args[0]", etc.) because the vertical lines want very much to snap to the vertical edges of the (borderless) text boxes instead of to the outer box. It's probably best if

• Vertical lines do not snap to horizontal connectors and vice-versa
• Corner connectors should probably not exist on borderless text boxes
• Lines do not snap to connectors unless the user is dragging the end of the line (i.e. doing a resize, not a move).

The exception in the screen shot is unrelated but caused me to lose some work, since clicking Continue seems to make the same exception again. I don't know what I did to cause it but here's the stack trace:

See the end of this message for details on invoking
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.ArgumentException: Parameter is not valid.
at System.Drawing.Pen.get_Width()
at FlowSharpLib.VerticalLine.get_UpdateRectangle()
at FlowSharpLib.GraphicElement.OnScreen()
at FlowSharpLib.BaseController.MoveElement(GraphicElement el, Point delta)
at FlowSharpLib.Line.MoveElementOrAnchor(GripType gt, Point delta)
at FlowSharpLib.CanvasController.<>c__DisplayClass8_0.b__0(Connection c)
at System.Collections.Generic.List1.ForEach(Action1 action)
at FlowSharpLib.CanvasController.DragSelectedElements(Point delta)
at FlowSharpLib.MouseController.DragShapes()
at FlowSharpLib.MouseController.b__66_21()
at FlowSharpLib.MouseController.<>c.b__67_1(MouseRouter r)
at System.Collections.Generic.List1.ForEach(Action1 action)
at FlowSharpLib.MouseController.HandleEvent(MouseAction action)
at FlowSharpLib.MouseController.b__64_2(Object sndr, MouseEventArgs args)
at System.Windows.Forms.Control.OnMouseMove(MouseEventArgs e)
at System.Windows.Forms.Control.WmMouseMove(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

Rather than using the PropertyGrid. Creating an editor window would be ideal.

If connection points of the group box and the inner children are too close together, a connector
snaps to the wrong connection point. Need to snap to the nearest connection, not just the first near connection.

Replace PropertyGrid with a user friendly toolbar.
Be able to show (enable) common properties of multiple selected shapes, disable properties not common to multiple selected shapes.

Doesn't seem right -- the anchor shouldn't bounce around as we traverse X and Y axes.

Being able to plug in shapes defined by others is going to a be a really useful feature for customization.
Technically, even the built-in shapes should be organized as a core plugin.

Select two shapes, change a property like color. Position, size, text -- all properties of both shapes are updated to the same values.

1. Create 2 shapes
2. Group one of the shapes.
3. Select the shape in the groupbox
4. Shift-clickdown-drag on the shape outside of the groupbox

Note how the shape inside the groupbox is dragged. This only happens when you start the dragging operation on the ungrouped shape without releasing the mouse button.

As a result of commit 59012fe connected lines no longer move when shape is moved.

The request has been made to be able to prevent auto-snapping, particularly when moving a line or connector manually via keyboard arrow keys.

This issue has been resolved by ignoring the snap check when the connector or line is moved while holding down the Ctrl key.

Nothing more to explain about this one.

Particularly for diagonal connectors, but dynamic connectors is general, the determination for selecting a connector should be based on whether the click point is near the line(s) rather than inside the overall display rectangle.

Create a box
Attach a vertical or horizontal line
Group the box

Observe how dragging the box results in trails and double-movement of the line.

If the document changes (shapes added / removed) or shape property changes, the document should be flagged as changed and should prompt user for saving changes before exit/new/load.

Combine a group of shapes to an "off page" connector shape and double-click to bring up the sub-shapes.

Minimizing the window with or without shapes on it is triggering this error from line 119 of Canvas.cs which is creating a new Bitmap with the height and width passed in. I noticed the height was set to 0 but this is not what is causing the exception as I hardcoded several other heights in which changed nothing. From what I've gathered on SO, it's most likely a memory issue, however, the SO questions I've located are really separate use cases of Bitmap() such as a file stream from a png file and an image size that was taking up like 1.3GB and the issue there was memory cap.

See the end of this message for details on invoking 
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.ArgumentException: Parameter is not valid.
   at System.Drawing.Bitmap..ctor(Int32 width, Int32 height, PixelFormat format)
   at System.Drawing.Bitmap..ctor(Int32 width, Int32 height)
   at FlowSharpLib.Canvas.CreateBitmap() in D:\Downloaded-Projects\FlowSharp\FlowSharpLib\Canvas.cs:line 119
   at FlowSharpLib.Canvas.<Initialize>b__26_0(Object sndr, EventArgs args) in D:\Downloaded-Projects\FlowSharp\FlowSharpLib\Canvas.cs:line 64
   at System.Windows.Forms.Control.OnResize(EventArgs e)
   at System.Windows.Forms.Panel.OnResize(EventArgs eventargs)
   at System.Windows.Forms.Control.OnSizeChanged(EventArgs e)
   at System.Windows.Forms.Control.UpdateBounds(Int32 x, Int32 y, Int32 width, Int32 height, Int32 clientWidth, Int32 clientHeight)
   at System.Windows.Forms.Control.UpdateBounds()
   at System.Windows.Forms.Control.WmWindowPosChanged(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)


************** Loaded Assemblies **************
mscorlib
    Assembly Version: 4.0.0.0
    Win32 Version: 4.6.1586.0 built by: NETFXREL2
    CodeBase: file:///C:/Windows/Microsoft.NET/Framework/v4.0.30319/mscorlib.dll
----------------------------------------
FlowSharp
    Assembly Version: 1.0.0.0
    Win32 Version: 1.0.0.0
    CodeBase: file:///D:/Downloaded-Projects/FlowSharp/bin/Debug/FlowSharp.exe
----------------------------------------
System.Windows.Forms
    Assembly Version: 4.0.0.0
    Win32 Version: 4.6.1586.0 built by: NETFXREL2
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Windows.Forms/v4.0_4.0.0.0__b77a5c561934e089/System.Windows.Forms.dll
----------------------------------------
System
    Assembly Version: 4.0.0.0
    Win32 Version: 4.6.1586.0 built by: NETFXREL2
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System/v4.0_4.0.0.0__b77a5c561934e089/System.dll
----------------------------------------
System.Drawing
    Assembly Version: 4.0.0.0
    Win32 Version: 4.6.1586.0 built by: NETFXREL2
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Drawing/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Drawing.dll
----------------------------------------
FlowSharpLib
    Assembly Version: 1.0.0.0
    Win32 Version: 1.0.0.0
    CodeBase: file:///D:/Downloaded-Projects/FlowSharp/bin/Debug/FlowSharpLib.DLL
----------------------------------------
System.Configuration
    Assembly Version: 4.0.0.0
    Win32 Version: 4.6.1586.0 built by: NETFXREL2
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Configuration/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Configuration.dll
----------------------------------------
System.Core
    Assembly Version: 4.0.0.0
    Win32 Version: 4.6.1586.0 built by: NETFXREL2
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Core/v4.0_4.0.0.0__b77a5c561934e089/System.Core.dll
----------------------------------------
System.Xml
    Assembly Version: 4.0.0.0
    Win32 Version: 4.6.1586.0 built by: NETFXREL2
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Xml/v4.0_4.0.0.0__b77a5c561934e089/System.Xml.dll
----------------------------------------
System.Drawing.Design
    Assembly Version: 4.0.0.0
    Win32 Version: 4.6.1586.0 built by: NETFXREL2
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/System.Drawing.Design/v4.0_4.0.0.0__b03f5f7f11d50a3a/System.Drawing.Design.dll
----------------------------------------
Accessibility
    Assembly Version: 4.0.0.0
    Win32 Version: 4.6.1586.0 built by: NETFXREL2
    CodeBase: file:///C:/WINDOWS/Microsoft.Net/assembly/GAC_MSIL/Accessibility/v4.0_4.0.0.0__b03f5f7f11d50a3a/Accessibility.dll
----------------------------------------

************** JIT Debugging **************
To enable just-in-time (JIT) debugging, the .config file for this
application or computer (machine.config) must have the
jitDebugging value set in the system.windows.forms section.
The application must also be compiled with debugging
enabled.

For example:

<configuration>
    <system.windows.forms jitDebugging="true" />
</configuration>

When JIT debugging is enabled, any unhandled exception
will be sent to the JIT debugger registered on the computer
rather than be handled by this dialog box.

As suggested in article comments.

This exception occurred while fussing with the vertical line shape. I haven't figured out how to reproduce it.

See the TODO in DiagonalConnector.cs

Create a shape and disconnected connector.
Select both.
Drag the shape.

Notice that the connector doesn't move!

This is the result of getting rid of the "MoveAnchorOrShape" (or whatever it was called) method.

Implement undo/redo feature.

Create two shapes and a connector attached to both shapes.
Group one of the shapes (without the connector)
Drag the surface.

Observe how the connector attached to the grouped shape disconnects and moves at 2x rate of canvas dragging.

A nice to have feature when working on documents that need to fit on specific page sizes.

Create a box and a connector attached to the box. Group both the box and the connector. Drag the groupbox. The connector's endpoint moves at 2x rate.

Lines are a weird situation, that I'm not actually happy with myself. The reason that lines only snap when dragging is that, if the endpoint snaps, then the entire line would have to be moved left-right or up-down. This may actually be acceptable behavior. Will consider.

Add a shape that auto-fits and image to the shape's dimensions.

In the update of about 20 hours ago, if you group together a box and anything else on top of that box, the group is impossible to move and impossible to duplicate, since clicking on the box selects the box, not the group. Even worse, it seems impossible to ungroup the group! The workaround is to select the box and delete it.

In fact, this problem occurs if you simply draw a box and group the box by itself.

Another comment: "Group" now has the unusual side-effect of creating an outer box. This is often useful for me, but it is not always useful. Perhaps there should be two grouping options, "Group in box" and just "Group" (which, consistent with other programs, does not create an outer box or creates an invisible outer box.)

Steps to reproduce

1. Place triangle on the canvas.
2. Change border width to 2
3. Change size to min height and resize the width left/right

As suggested by reader comments.

Currently you have to save as a PNG and then print the PNG with a separate tool.
Dealing with multiple page layout, as well as centering on page, or shrinking to fit on page are must have features.

Other than arrows and diamonds.

I'm drawing a diagram with boxes nested inside other boxes. While trying to resize the outer box, if an inner box is nearby then FlowSharp tends to prefer to drag that object instead, even if the resize handles of the selected box are closer to the mouse!

Select a shape, then click on the canvas. The shape is deselected but the property grid still shows the properties for the shape.

Related to snapping to grid spacing, changing the grid spacing would be useful.

Real routing, multiple corners, and automatic routing around shapes.

Click on shape
Click on a field in the property grid and change it's value

Notice what you type appears in the edit box of the shape!

How to recover gracefully from an exception, particularly one that persists because of an error with a drawing parameter. See Issue #32 for a screenshot example.

Select a shape (click)
Click-hold and drag
Release mouse button

Notice property grid is empty.

In fact, notice on mouse-down of the second click, the property grid goes empty.

DONE: Corners and justification would be nice.
Text should also be clipped to not exceed extents of shape.
Multi-line text.
Connectors don't support text.
Text location for connectors.

As suggested in article comments.

Currently, only the first discovered shape is selected. For overlapping shapes, it would be nice to rotate the selection between all shapes that qualify as selectable. This requires figuring out how to display a shape underneath another shape.

Drop a triangle, add a connector to one of the center connector points, resize the triangle. The connector snaps to a different connection point. Seem to only happen with triangle shapes.

Implement custom connection points.
Connection points should adjust proportionally when shape is sized.

Create a big box
Create a small box and drag it into the big box
Shift-click to select the big box
Ctrl+C
Ctrl+V

Notice that the big box is now on top, you have to move its z-order to the bottom for the little box to appear.

1. Create a box
2. Group the box
3. Attach a connector to a box's connection point (note that you can't attach the connector to the groupbox because the snap is too aggressive)

Observe that when the groupbox is moved, the connector double-moves.