Hi,
maybe it’s a late response, but hopefully it will benefit someone.
I will build on your code, will try to make my code very explicit, to be easy to understand.
Next, you will find 2 code blocks:
- the code with resize working as intended.
- same as the first one, but added the visual feed back part, to make it feel professional
.
Final Result:

First Block
import sys
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
FREE_STATE = 1
BUILDING_SQUARE = 2
BEGIN_SIDE_EDIT = 3
END_SIDE_EDIT = 4
class MyWidget(QWidget):
def __init__(self):
super().__init__()
self.setGeometry(30, 30, 600, 400)
self.begin = QPoint()
self.end = QPoint()
self.state = FREE_STATE
def paintEvent(self, event):
qp = QPainter(self)
br = QBrush(QColor(100, 10, 10, 40))
qp.setBrush(br)
qp.drawRect(QRect(self.begin, self.end))
def mousePressEvent(self, event):
if not self.begin.isNull() and not self.end.isNull():
p = event.pos()
y1, y2 = sorted([self.begin.y(), self.end.y()])
if y1 <= p.y() <= y2:
# 3 resolution, more easy to pick than 1px
if abs(self.begin.x() - p.x()) <= 3:
self.state = BEGIN_SIDE_EDIT
return
elif abs(self.end.x() - p.x()) <= 3:
self.state = END_SIDE_EDIT
return
self.state = BUILDING_SQUARE
self.begin = event.pos()
self.end = event.pos()
self.update()
def applye_event(self, event):
if self.state == BUILDING_SQUARE:
self.end = event.pos()
elif self.state == BEGIN_SIDE_EDIT:
self.begin.setX(event.x())
elif self.state == END_SIDE_EDIT:
self.end.setX(event.x())
def mouseMoveEvent(self, event):
self.applye_event(event)
self.update()
def mouseReleaseEvent(self, event):
self.applye_event(event)
self.state = FREE_STATE
if __name__ == '__main__':
app = QApplication(sys.argv)
window = MyWidget()
window.show()
app.aboutToQuit.connect(app.deleteLater)
sys.exit(app.exec_())
Second Block
import sys
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
FREE_STATE = 1
BUILDING_SQUARE = 2
BEGIN_SIDE_EDIT = 3
END_SIDE_EDIT = 4
CURSOR_ON_BEGIN_SIDE = 1
CURSOR_ON_END_SIDE = 2
class MyWidget(QWidget):
def __init__(self):
super().__init__()
self.setGeometry(30, 30, 600, 400)
self.begin = QPoint()
self.end = QPoint()
self.state = FREE_STATE
self.setMouseTracking(True)
self.free_cursor_on_side = 0
def paintEvent(self, event):
qp = QPainter(self)
br = QBrush(QColor(100, 10, 10, 40))
qp.setBrush(br)
qp.drawRect(QRect(self.begin, self.end))
if not self.free_cursor_on_side:
return
qp.setPen(QPen(Qt.black, 5, Qt.DashLine))
if self.free_cursor_on_side == CURSOR_ON_BEGIN_SIDE:
end = QPoint(self.end)
end.setX(self.begin.x())
qp.drawLine(self.begin, end)
elif self.free_cursor_on_side == CURSOR_ON_END_SIDE:
begin = QPoint(self.begin)
begin.setX(self.end.x())
qp.drawLine(self.end, begin)
def cursor_on_side(self, e_pos) -> int:
if not self.begin.isNull() and not self.end.isNull():
y1, y2 = sorted([self.begin.y(), self.end.y()])
if y1 <= e_pos.y() <= y2:
# 5 resolution, more easy to pick than 1px
if abs(self.begin.x() - e_pos.x()) <= 5:
return CURSOR_ON_BEGIN_SIDE
elif abs(self.end.x() - e_pos.x()) <= 5:
return CURSOR_ON_END_SIDE
return 0
def mousePressEvent(self, event):
side = self.cursor_on_side(event.pos())
if side == CURSOR_ON_BEGIN_SIDE:
self.state = BEGIN_SIDE_EDIT
elif side == CURSOR_ON_END_SIDE:
self.state = END_SIDE_EDIT
else:
self.state = BUILDING_SQUARE
self.begin = event.pos()
self.end = event.pos()
self.update()
def applye_event(self, event):
if self.state == BUILDING_SQUARE:
self.end = event.pos()
elif self.state == BEGIN_SIDE_EDIT:
self.begin.setX(event.x())
elif self.state == END_SIDE_EDIT:
self.end.setX(event.x())
def mouseMoveEvent(self, event):
if self.state == FREE_STATE:
self.free_cursor_on_side = self.cursor_on_side(event.pos())
if self.free_cursor_on_side:
self.setCursor(Qt.SizeHorCursor)
else:
self.unsetCursor()
self.update()
else:
self.applye_event(event)
self.update()
def mouseReleaseEvent(self, event):
self.applye_event(event)
self.state = FREE_STATE
if __name__ == '__main__':
app = QApplication(sys.argv)
window = MyWidget()
window.show()
app.aboutToQuit.connect(app.deleteLater)
sys.exit(app.exec_())
regards.