[EXA] Audacity scrolling/zooming when zoomed in is painfully slow

Submitted by S. Christian Collins

Assigned to xf86-video-ati maintainers

Link to original bug (#93541)

Description

Here is a video I made demonstrating this bug:
https://youtu.be/Mr7H1oy0x8Y

Steps to reproduce:

1. Open Audacity.
   
2. Drag an audio file into Audacity, preferably something at least a minute in length.
   
3. Use CTRL-mouse wheel to zoom in a little bit.
   
4. Drag the horizontal scrollbar back and forth. You should see smooth movement.
   
5. Zoom in further, even up to the sample level, but you don't need to go that far. You should notice the zooming operation start to get laggy.
   
6. Drag the horizontal scrollbar back and forth.
   

Result: The scrolling is unbearably choppy. On my system, the scrolling operation eats up an entire CPU core.

Expected result: The scrolling should be smooth and not eat an entire CPU core.

** My System **
OS: Kubuntu 14.04 64-bit w/ KDE SC 4.14.13
PC: HP Pavilion m6-1035dx
CPU/GPU: AMD A10-4600M APU with Radeon HD 7660G Graphics
RAM: 6GB DDR3 800 MHz
Linux Kernel: 3.16.0-57-generic
Screen Resolution: 1366 x 768

I have also tested this using a Kubuntu 15.10 live USB with the same results (not sure of kernel/xorg version used). I will be happy to do more tests if necessary.