Fix rectangle selection edge not follow mouse
Summary:
- In rectangle mode, when to adjust selection, the right, bottom edge not follow mouse
- Fix wrong rectangle size
Test Plan:
- In rectangle mode, adjust the ( topright, right, bottom right, bottom, bottom left) selection and check mouse and edge position.
2 select full screen and check size
3 save image and check image size
Reviewers: Spectacle, rkflx, ngraham
Reviewed By: Spectacle, rkflx, ngraham
Subscribers: rkflx, ngraham
Differential Revision: https://phabricator.kde.org/D11598