Include missing header QStyle

[qianyueyou]

To fix build error.

[carsonip]

Sorry I'm quite busy these days, hopefully I can pull up the build tools and try your PR during the weekends.

[carsonip]

I just looked into the code. I actually used QStyle without including it in the first place. Not sure how it compiled successfully in the past (on my machine and Travis CI). Your edit should be ok, but I'm curious about what build error you got. Do you have the logs?

[qianyueyou]

Hey I was building on Linux, and it was a simple unknown identifier error. Searching online reveals that it might have to do with their internal header dependency cleanup in qt5.

src/mainwindow.cpp: In constructor ‘MainWindow::MainWindow(QWidget*)’:                                         
src/mainwindow.cpp:104:21: error: incomplete type ‘QStyle’ used in nested name specifier                       
             QStyle::alignedRect(Qt::LeftToRight, Qt::AlignCenter, this->size(),                               
                     ^~~~~~~~~~~
src/mainwindow.cpp: In member function ‘virtual void MainWindow::paintEvent(QPaintEvent*)’:                    
src/mainwindow.cpp:258:42: warning: unused parameter ‘event’ [-Wunused-parameter]                              
 void MainWindow::paintEvent(QPaintEvent *event) {
                             ~~~~~~~~~~~~~^~~~~
src/mainwindow.cpp: In member function ‘virtual void MainWindow::mouseReleaseEvent(QMouseEvent*)’:             
src/mainwindow.cpp:293:49: warning: unused parameter ‘event’ [-Wunused-parameter]                              
 void MainWindow::mouseReleaseEvent(QMouseEvent *event) {                                                      
                                    ~~~~~~~~~~~~~^~~~~
src/mainwindow.cpp: In member function ‘virtual void MainWindow::enterEvent(QEvent*)’:                         
src/mainwindow.cpp:302:37: warning: unused parameter ‘event’ [-Wunused-parameter]                              
 void MainWindow::enterEvent(QEvent *event) {
                             ~~~~~~~~^~~~~
src/mainwindow.cpp: In member function ‘virtual void MainWindow::leaveEvent(QEvent*)’:                         
src/mainwindow.cpp:308:37: warning: unused parameter ‘event’ [-Wunused-parameter]                              
 void MainWindow::leaveEvent(QEvent *event) {
                             ~~~~~~~~^~~~~
src/mainwindow.cpp: In member function ‘virtual void MainWindow::resizeEvent(QResizeEvent*)’:                  
src/mainwindow.cpp:313:44: warning: unused parameter ‘event’ [-Wunused-parameter]                              
 void MainWindow::resizeEvent(QResizeEvent *event) {
                              ~~~~~~~~~~~~~~^~~~~

[carsonip]

Makes sense. Thanks for the PR!