Smoothly scroll text (like breaking news…)

问题

Note: This question is created to help others find what I could not find, having said that anyone is welcome to propose a better solution than I came up with.

My challenge was to produce a smooth scrolling text stream on a windows form application, in addition the form had other items drawn on it so I had to avoid destroying them in the process.

I tried moving a text box incrementing it with timers and do...loops and so on, also tried using Graphics.DrawString again incrementing the position. All of them produced a jerky output with the text flashing as it moved.

I Spent several hours googling and browsing probably in the region of 50 different proposed solutions including many in other languages in the hope I might get a clue!

I can't identify which one gave me the clue but I saw several references to Doublebuffer so I googled that (and tried it without sucess!) and finally came up with the idea from here of a manual buffer so I ended up with....(see answer below)

回答1:

Do
        Dim currentContext As BufferedGraphicsContext
        Dim myBuffer As BufferedGraphics
        ' Gets a reference to the current BufferedGraphicsContext.
        currentContext = BufferedGraphicsManager.Current
        ' Creates a BufferedGraphics instance associated with Form1, and with 
        ' dimensions the same size as the drawing surface of Form1.
        myBuffer = currentContext.Allocate(BNP1.CreateGraphics, BNP1.DisplayRectangle)
        'update test
        With myBuffer
            .Graphics.Clear(Panel.BackColor)
            .Graphics.DrawString("Some Text", [Your Font], Brushes.Blue, xpos, ypos)
        End With
        myBuffer.Render()
        myBuffer.Dispose()
        'This bit will need adjusting to suit your layout!
        If xpos + Panel.Width < Panel.Left Then xpos = Panel.Right Else xpos -= 1
        Thread.Sleep(1)
Loop

This produced a perfectly smooth scroll with a fully adjustable scroll speed using the sleep time and xpos reduction.

As you will probably notice I did this with a Do...Loop in a separate thread it also works in a timer but the scroll speed for some reason (someone can probably explain) is much slower.

Disclaimer: I am not a professional coder so if anyone has suggestions to improve what I have done I will greatly appreciate it (avoid generics such as Option Strict - already on!)

来源：https://stackoverflow.com/questions/35700597/smoothly-scroll-text-like-breaking-news

标签

vb.net

winforms

buffer