In Qt scribble example (located in Qt examples/widgets/scribble/), user can draw any shape with pen color and pen width with mouse event.
void ScribbleArea::mouseMoveEvent(QMouseEvent *event)
{
if ((event->buttons() & Qt::LeftButton) && scribbling)
drawLineTo(event->pos());
}
void ScribbleArea::mouseReleaseEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton && scribbling) {
drawLineTo(event->pos());
scribbling = false;
}
}
In the original example, the line drawn cannot be modified any more. I want to change it so that I can change line color/width after the lines are drawn, and also save the drawing as a "draft" so line color/width can be edited even open later.
My first thought is to save the points from mouse event and redraw shape every time an edit happens. There may be a lot of data to process if the drawing is not small and redrawing everything seems poor in efficiency. Is there a more elegant way out there to do this? Thank you.
Related
So a few years ago, I wrote a custom touchscreen driver specifically for a particular application which ran on a Scientific Linux 6.4 (CentOS 6 based) OS, which did not have native touch support, but the kernel supported touch events, so I was able to directly read the raw data from the touchscreen in /dev/input/event* and read the event data to generate mouse events with Qt to control the application to mimic a multi-touch touchscreen. More recently, we've finally migrated to RedHat 8.4, but I had to disable the native touch driver, because as far as I know, the native Qt touch events didn't allow the same degree of control over the application that my driver did.
Recently during a trial, a technician reported that when using the touchscreen to manipulate one of the application's image display areas, the movement was very "jittery". The image display area is simply a QScrollArea with a QImage inside, and hidden scroll bars. The way it works is that on a mouseMoveEvent, it manipulates the scrollbars according to the delta value on the mouse event.
void PanArea::mouseMoveEvent(QMouseEvent* e)
{
SafeStr str;
if (m_pw)
{
if (m_disable_panning == false &&
e->buttons().testFlag(Qt::RightButton))
{
QPoint delta = e->pos() - m_last_pos;
horizontalScrollBar()->setValue(horizontalScrollBar()->value() -
delta.x());
verticalScrollBar()->setValue(verticalScrollBar()->value() -
delta.y());
m_last_pos = e->pos();
emit signalScrollPositionChanged(getScrollPosition());
// This force update has been added because
// when fast panning cause black to appear within the image
// because some pan widget updates were being skipped.
// Performance seems acceptable with this here.
m_pw->update();
}
else if (...)
{
// irrelevant code removed to save space
}
}
}
This works fine when simply right-click dragging on the scroll area. And then here is the relevant function that dispatches the mouse press and mouse move events from the touchscreen driver:
void InputHandler::panStart(TouchPoint* tp, QWidget* widget)
{
QPoint pos(tp->cx(), tp->cy());
QWidget* target = widget;
if (target == NULL) target = QApplication::widgetAt(pos);
if (target != NULL)
{
QPoint local = target->mapFromGlobal(pos);
QMouseEvent* press =
new QMouseEvent(QEvent::MouseButtonPress, local, pos,
Qt::RightButton, Qt::RightButton, Qt::NoModifier);
QApplication::postEvent(widget, press);
}
}
void InputHandler::panMove(TouchPoint* tp, QWidget* widget)
{
QPoint pos(tp->cx(), tp->cy());
QWidget* target = widget;
if (target == NULL) target = QApplication::widgetAt(pos);
if (target != NULL)
{
QPoint local = target->mapFromGlobal(pos);
QMouseEvent* move =
new QMouseEvent(QEvent::MouseMove, local, pos, Qt::NoButton,
Qt::RightButton, Qt::NoModifier);
QApplication::postEvent(widget, move);
}
}
When I touch and drag on the widget, it DOES move, but it jumps all over the place as if I were rapidly dragging it in random directions.
Is there some caveat of how Qt5 mouse events work that could explain this behavior? Or something to do with the way the widget is moving the image around?
I created my own classes (view and scene) to display image and objects I added to it, even got zoom in/out function implemented to my view, but now I have to add new functionality and I don't even know how to start looking for it.
Whenever I press the scroll button of my mouse and hold it - I wish to move around the scene, to see different parts of it - just like I would with sliders. It is supposed to be similar to any other program allowing to zoom in/out to image and move around zoomed picture to see different parts of it.
Unfortunately - I don't even know how to look for some basic, because "moving" and similar refer to dragging objects around.
EDIT 1
void CustomGraphicView::mouseMoveEvent(QMouseEvent *event)
{
if(event->buttons() == Qt::MidButton)
{
setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
translate(event->x(),event->y());
}
}
Tried this - but it is working in reverse.
I suppose you know how to handle events using Qt.
So, to translate (move) your view use the QGraphicsView::translate() method.
EDIT
How to use it:
void CustomGraphicsView::mousePressEvent(QMouseEvent* event)
{
if (e->button() == Qt::MiddleButton)
{
// Store original position.
m_originX = event->x();
m_originY = event->y();
}
}
void CustomGraphicsView::mouseMoveEvent(QMouseEvent* event)
{
if (e->buttons() & Qt::MidButton)
{
QPointF oldp = mapToScene(m_originX, m_originY);
QPointF newP = mapToScene(event->pos());
QPointF translation = newp - oldp;
translate(translation.x(), translation.y());
m_originX = event->x();
m_originY = event->y();
}
}
I am new to MFC trying to learn from the scratch.
I am trying to create a small dialog based application in VS2012 - MFC.
On the dialog window i have drawn a rectangle (in OnPaint event) like this.
CPaintDC dc(this);
CRect background1(10,10,208,92);
dc.Rectangle(10,10,208,92);
Then i filled the bacground with some color. Like this.
CBrush brush1;
brush1.CreateSolidBrush(RGB(2,3,4));
dc.FillRect(background1,&brush1);
Now i wanted to draw waves in form of pixels continuously inside the rectangle.
As of now what i have done is,
bool top = false;
for(i=10,j=92;i<200 && j>10;)
{
pDC->SetPixel(i,j,NewColor);
Sleep(10);
if(!top)
j-=1;
else
j+=1;
if(j%4==0)
{
i+=1;
}
if(j==12)
top=true;
if(j==90)
top = false;
}
I am just drawing the pixels straightaway on the window, but within the dimensions where the rectangle lies. And the waves stop as it reaches the right dimension of the rect. But i feel thats not the right way to do it.
I want to draw the waves inside the rectangle and also continuosly, like when it reacahes the right end it should move left and it should be continuous.
Is there any proper way in MFC to draw something inside a rectangle (technically inside another object)?
Please help me out.
The ScrollWindow function can be used to scroll the existing graph to the left. Then you draw the new data to the right of the scrolled area. The drawing will be much faster if you use the Polyline function instead of DrawPixel: Polyline draws an array of pixels.
I tried your code and just added some condition, so that if it reaches right side it should start moving toward left.
void CMyDlg::OnBnClickedOk()
{
CWnd *cWnd = FromHandle(m_hWnd);
CDC *pDC = cWnd->GetDC();
bool top = false;
bool right = false;
int i,j;
for(i=10,j=92;i<=200 && j>10;)
{
pDC->SetPixel(i,j,RGB(255,255,255));
Sleep(10);
if(!top)
j-=1;
else
j+=1;
if(j%4==0)
{
if(!right)
i++; // if reaches right side i--;
else{
i--;
}
}
if(j==12)
top=true;
else if(j==90)
top = false;
if(i == 200)// make right = true if reaches right side
right = true;
else if(i == 10)// make false it reaches left side
right = false;
}
}
I am getting output something like this
NOTE: this will cause infinite loop, you need to check condition where you have to stop printing pixels.
You are NOT looping with Sleep(10) in your WM_PAINT handler, are you?
MFC or not, you should separate your data processing from presentation.
It appears you are trying to do an animation; the simplest way to do it is to have an off-screen (memory) DC and drawing your pixels on it. At certain times (frame rate?), you would call parent's InvalidateRect()/UpdateWindow() pair. Then in ON_PAINT, you would BitBlt() your prepared DC onto your preferred location in the dialog.
What I'm trying to do is:
I have a sprite. And this sprite has 3 textures. First texture, let's call it "not-visited", is the initial one. Now, when I click on the sprite it should change it texture to "clicked" meaning that the sprite was clicked. And this texture should remain until I click somewhere else on the screen. When I do this, the texture should change to the third one, "visited". And if I click on the sprite again it should change its texture to "clicked"...
So, I should have here a bool function called "ClickDetected" and its code should do this:
if (event.type == Event::MouseButtonReleased && event.mouseButton.button == Left)
if (mouse_over_sprite)
return true;
Right? OK, then, I have a class Node. This class has a method "Clicked":
bool Clicked {
if (ClickDetected) { return true; }
}
I know it may be unnecessary, but let it stay for now. Next, in Update() method of this class:
if (Clicked) { change_texture_to_"clicked"; if (!visited) visited=true; }
else {
if (!visited) change_texture_to_"not-visited";
if (visited) change_texture_to_"visited";
}
But this doesn't work how it should. When I click on sprite texture changes to "clicked". When I release the mouse button the "clicked" texture stays... But when I move the mouse texture changes to "visited". And it should remain "clicked", until I click somewhere else. I tried to use a while loop here, but it didn't work. What can I do?
I've put this code to Graph class (method Update()) to manage many Nodes. I've change it a little bit and now it works fine.
I need to get the color of pixel under mouse, inside mouseMoveEvent of a QWidget (Breadboard). Currently I have this code->
void Breadboard::mouseMoveEvent(QMouseEvent *e)
{
QPixmap pixmap = QPixmap::grabWindow(winId());
QRgb color = pixmap.toImage().pixel(e->x(), e->y());
if (QColor(color) == terminalColor)
QMessageBox::information(this, "Ter", "minal");
}
Take a look at (scaled down) screenshot below-
When user moves his mouse on breadboard, the hole should get highlighted with some different color (like in red circle). And when the mouse exits, the previous color (grey) should be restored. So I need to do following steps-
Get color under mouse
According to color, floodfill the hole. (Different holes are distinguished using color)
On mouse out, restore the color. There would be wires going over holes, so I can't update the small rectangle (hole) only.
What is the fastest way of doing this? My attempt to extract color is not working i.e the Message box in my above code never displays. Moreover I doubt if my existing code is fast enough for my purpose. Remember, how fast you will be moving your mouse on breadboard.
Note - I was able to do this using wxWidgets framework. But due to some issues that project got stalled. And I am rewriting it using Qt now.
You are invited to look at code https://github.com/vinayak-garg/dic-sim
The "idiomatic" way of doing this in Qt is completely different from what you're describing. You'd use the Graphics View Framework for this type of thing.
Graphics View provides a surface for managing and interacting with a large number of custom-made 2D graphical items, and a view widget for visualizing the items, with support for zooming and rotation.
You'd define your own QGraphicsItem type for the "cells" in the breadboard that would react to hover enter/leave events by changing their color. The connections between the cells (wires, resistors, whatever) would also have their own graphics item types with the features you need for those.
Here's a quick and dirty example for you. It produces a 50x50 grid of green cells that become red when the mouse is over them.
#include <QtGui>
class MyRect: public QGraphicsRectItem
{
public:
MyRect(qreal x, qreal y, qreal w, qreal h)
: QGraphicsRectItem(x,y,w,h) {
setAcceptHoverEvents(true);
setBrush(Qt::green);
}
protected:
void hoverEnterEvent(QGraphicsSceneHoverEvent *) {
setBrush(Qt::red);
update();
}
void hoverLeaveEvent(QGraphicsSceneHoverEvent *) {
setBrush(Qt::green);
update();
}
};
int main(int argc, char **argv)
{
QApplication app(argc, argv);
QGraphicsScene scene;
for (int i=0; i<50; i++)
for (int j=0; j<50; j++)
scene.addItem(new MyRect(10*i, 10*j, 8, 8));
QGraphicsView view(&scene);
view.show();
return app.exec();
}
You could modify the hover event handlers to talk to your "main window" or "controller" indicating what's currently under the mouse so you can update your caption, legend box or tool palette.
For best speed, render only the portion of the widget you're interested in into a QPaintDevice (like a QPixmap). Try something like this:
void Breadboard::mouseMoveEvent(QMouseEvent *e)
{
// Just 1 pixel.
QPixmap pixmap(1, 1);
// Target coordinates inside the pixmap where drawing should start.
QPoint targetPos(0, 0);
// Source area inside the widget that should be rendered.
QRegion sourceArea( /* use appropriate coordinates from the mouse event */ );
// Render it.
this->render(&pixmap, targetPos, sourceArea, /* look into what flags you need */);
// Do whatever else you need to extract the color from the 1 pixel pixmap.
}
Mat's answer is better if you're willing to refactor your application to use the graphics view API.