ImSequencer - Zooming with mouse wheel at cursor position

[nyaki-HUN]

I know this feature is currently defined out in the code, but here is a working version I am using which can perform zooming in/out at the cursor position properly with the mouse wheel.

                    int frameOverCursor = (int)((io.MousePos.x - topRect.Min.x) / framePixelWidth) + firstFrameUsed;
                    if (io.MouseWheel < -FLT_EPSILON)
                    {
                        framePixelWidthTarget *= 0.9f;
                        framePixelWidth *= 0.9f;
                        int newFrameOverCursor = (int)((io.MousePos.x - topRect.Min.x) / framePixelWidth) + firstFrameUsed;
                        *firstFrame += frameOverCursor - newFrameOverCursor;
                    }

                    if (io.MouseWheel > FLT_EPSILON)
                    {
                        framePixelWidthTarget *= 1.1f;
                        framePixelWidth *= 1.1f;
                        int newFrameOverCursor = (int)((io.MousePos.x - topRect.Min.x) / framePixelWidth) + firstFrameUsed;
                        *firstFrame += frameOverCursor - newFrameOverCursor;
                    }

[CedricGuillemet]

Sounds like a good fix. Could you please do a PR for that?

[nyaki-HUN]

There you go.

Also I kept the #if 0 block around the code in the PR just to make sure I won't break anything for someone, because zooming can collide with using the scrollbar.
Maybe a new option flag will be required later to set correct behavior and disable the scrollbar.