I am facing an issue while developing an application in Xojo, and I am seeking assistance here.
Problem Description: In my application, I am using a Canvas to display an image and have added horizontal and vertical scrollbars to enable image scrolling. However, when I scroll the image using the scrollbars, the image exceeds its expected range by a significant margin, approximately 3 times the canvas width. This prevents users from properly viewing the entire image.
Expected Outcome: I would like the image to stay within the bounds of the Canvas while scrolling, without exceeding its expected range.
Relevant Code Snippet: In the
Paint event of the application, I draw the image, and in the
Resizing event, I set the maximum and current values for the scrollbars.
Sub Paint(g As Graphics, areas() As Rect) ' Get the visible size of the Canvas Dim canvasVisibleWidth As Integer = imgCanvas.Width Dim canvasVisibleHeight As Integer = imgCanvas.Height ' Calculate the maximum values for horizontal and vertical scrollbars Dim hMax As Integer = Max(imgWidth - canvasVisibleWidth, 0) Dim vMax As Integer = Max(imgHeight - canvasVisibleHeight, 0) ' Ensure scrollbar values stay within the image range hScrollBar.MaximumValue = hMax hScrollBar.Value = Min(hScrollBar.Value, hMax) vScrollBar.MaximumValue = vMax vScrollBar.Value = Min(vScrollBar.Value, vMax) ' Draw the image on the Canvas, taking scrollbar position into account Dim xOffset As Integer = hScrollBar.Value Dim yOffset As Integer = vScrollBar.Value g.DrawPicture(imgCanvas.Backdrop, -xOffset, -yOffset) End Sub
I have tried various approaches to resolve this issue, but so far, none have been successful. I suspect there might be an error in calculating the maximum and current values for the scrollbars.
I would greatly appreciate any help and guidance from the community. Thank you very much!