1. Implement partial refresh.
2. Implement refresh canceling mechanism.
3. Refactor some parts of the gui and display code.
ad 1.
- Detect parts of the screen changed since last update and merge them
into bigger regions. These regions defines parts of the context sent
to the display.
- Refresh the region covering all of the parts since this is the most
time consuming part and the size of the refreshed region doesn't
change the time much.
- Refresh the whole screen if deep refresh is requested and previously
fast refresh was used. This is needed to prevent unwanted artifacts
in some cases.
ad 2.
- Separate display update and refresh logic.
- Divide image display message handling into two handlers, one updating
and other one refreshing the screen.
- Add cancel refresh message and use it to cancel refresh during update.
- Store sum of refresh regions gathered during updates to refresh them
all at once at the end.
Detect parts of the screen changed since last update and merge them into
bigger regions. These regions defines parts of the context sent to the
display.
Refresh the region covering all of the parts since this is the most time
consuming part and the size of the refreshed region doesn't change the
time much.
Refresh the whole screen if deep refresh is requested and previously
fast refresh was used. This is needed to prevent unwanted artifacts in
some cases.
Refactor some parts of the gui and display code.
