I have discovered that geometry->setLineWidth(3); in the code below extends to other QML elements and can distort them, even if those other QML elements are "normal" QML elements (with no QQuickItem subclass beneath them). This seems odd to me that you could affect other elements and I wonder if it is a bug? The documentation says that this function should only affect the current element, but that is not my experience. Can anyone weigh in on why geometry->setLineWidth(3); has such unwieldy power?
QSGNode *updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *data){
QSGGeometry *geometry =
new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), 2);
geometry->setDrawingMode(GL_LINES);
geometry->setLineWidth(3);
geometry->vertexDataAsPoint2D()[0].set(0, 0);
geometry->vertexDataAsPoint2D()[1].set(width(), height());
QSGFlatColorMaterial *material = new QSGFlatColorMaterial;
material->setColor(QColor(255, 0, 0));
QSGGeometryNode *node = new QSGGeometryNode;
node->setGeometry(geometry);
node->setFlag(QSGNode::OwnsGeometry);
node->setMaterial(material);
node->setFlag(QSGNode::OwnsMaterial);
delete oldNode;
return node;
}
If I omit the line geometry->setLineWidth(3); then the problem goes away.
I think it's a bug, sort of. The implementation in gsgbatchrenderer.cpp looks like this:
if (g->drawingMode() == GL_LINE_STRIP || g->drawingMode() == GL_LINE_LOOP || g->drawingMode() == GL_LINES)
glLineWidth(g->lineWidth());
The gl functions are global on the current OpenGL context so they apply to all drawing commands, and there's nothing that sets glLineWidth back to its previous value. However, any other nodes that also are in GL_LINES mode will also set the line width when it's their turn to render. So I'm guessing the other QML elements must be rendering lines without going through this code and setting the glLineWidth themselves. If I'm right then that's the bug and those other elements need to explicitly set the width.
Can you tell us what type those other 'normal' QML elements are?
Related
Is it possible for QTextLayout to render several characters, but to process/handle it as one character. For example rendering a code point like: [U+202e], and when moving the caret/calculating positions, it is treated as one character.
Edited:
Please check this following issue, were I explain what I'm trying to do. It for the edbee Qt component. It's using QTextLayout for line rendering.
https://github.com/edbee/edbee-lib/issues/127
Possibly it isn't possible with QTextLayout, the documentation is quite limited.
According to Qt docs:
"The class has a rather low level API and unless you intend to implement your own text rendering for some specialized widget, you probably won't need to use it directly." - https://doc.qt.io/qt-5/qtextlayout.html#details
You should probably use a QLineEdit or a QTextEdit (each has a method called setReadOnly(bool)).
Before answering the question, I will point out that the CursorMode enum (https://doc.qt.io/qt-5/qtextlayout.html#CursorMode-enum) seems very promising for this problem, but to me, the documentation isn't clear on how to use it or set it.
Now to answer your question in regards to QLineEdit or QTextEdit, it's a bit complicated, but it's the same for QLineEdit and QTextEdit, so lets look at QTextEdit.
Firstly, mouse clicks: QTextEdit has a signal called cursorPositionChanged(), which will be helpful here. You'll want to connect that to a custom slot, which can make use of the function moveCursor(QTextCursor::MoveOperation operation, QTextCursor::MoveMode mode = QTextCursor::MoveAnchor) (https://doc.qt.io/qt-5/qtextedit.html#moveCursor). Notice that there are very helpful enumeration values for you here in QTextCursor::MoveOperation regarding word hopping (https://doc.qt.io/qt-5/qtextcursor.html#MoveOperation-enum). How do we put all of this together? Well, probably the right way to do it is to determine the width of the chars to the left of the cursor's position and the width of the chars to the right of the cursor's position when the cursorPositionChanged() signal is emitted and go to the side of the word that has less width. However, I'm not sure how to do that. At this point I'd settle with checking the number of chars to the left and right and going to the side with less.
Secondly, keyboard presses: This goes a bit out of my knowledge, but almost everything drawable and iteractable inherits from QWidget. Take a look at https://doc.qt.io/qt-5/qwidget.html#keyPressEvent and it's possible that overriding that in your own implementation of QTextEdit is necessary to get the left arrow and right arrow keypresses to jump words (once you get that part it's pretty easy, just use the same function as last section for moving the cursor, or in the case of QLineEdit, cursorWordForward()/cursorWordBackward()).
All this being said, I've so far been assuming that you're not deleting anything or selecting anything. Selection can be a real pain depending on if you allow multiple selections, but the functions are all there in the documentation to implement those things.
Example of mouse click impl:
myclass.hpp
#include <QTextEdit>
#include <QTextCursor>
#include <QObject>
#include <QString>
int distance_to_word_beginning_or_end(const QString &str, int index, bool beginning);
class MyClass {
MyClass();
~MyClass();
private:
QTextEdit *text_edit;
public slots:
void text_edit_changed_cursor_location();
};
myclass.cpp
#include "myclass.hpp"
int distance_to_word_beginning_or_end(const QString &str, int index, bool beginning)
{
// return the distance from the beginning or end of the word from the index given
int inc_or_dec = (beginning) ? -1 : 1;
int distance = 0;
while (index >= 0 && index < str.length())
{
if (str.at(index) == ' ' || str.at(index) == '\n' || str.at(index) == '\t')
{
return distance;
}
distance++;
index += inc_or_dec;
}
return --distance;
}
MyClass::MyClass()
{
text_edit = new QTextEdit();
QObject::connect(text_edit, &QTextEdit::cursorPositionChanged, this, &MyClass::text_edit_changed_cursor_location);
}
MyClass::~MyClass()
{
delete text_edit;
}
void MyClass::text_edit_changed_cursor_location()
{
QString text_edit_string = text_edit->text();
QTextCursor text_edit_cursor = text_edit->textCursor();
auto current_position = text_edit_cursor.position();
QTextCursor new_text_cursor;
int distance_to_beginning = distance_to_word_beginning_or_end(text_edit_string, current_position, true);
int distance_to_end = distance_to_word_beginning_or_end(text_edit_string, current_position, false);
auto movement_type;
if (distance_to_beginning > distance_to_end)
{
new_text_cursor.setPosition(current_position + distance_to_end);
} else {
new_text_cursor.setPosition(current_position - distance_to_beginning);
}
text_edit->setTextCursor(new_text_cursor);
}
recently i start to learn Qt and now i'm working on GCS project that it must have a map with some tiled imges and and some graphics item like Plan,the path and also on over off all some gauge.
so we have 3 kind of item:
Tiled map in the background so that its change by scrolling .
in the middle there is a picture of airplane that move by gps changes and also its way .
on the all on off these items there 3 or 4 gauge like speed meter, horizontal gauge and altimeter gauge there are must be solid in somewhere of graphicsview and not change when scrolling down/up or left right
The question is what is the best way to implement this ?
here is first look of my project:
in first look gauge are not over map but i want to be ! i want to have bigger map screen with gauges include it !
And here is map updater code :
void mainMap::update()
{
m_scene->clear();
QString TilePathTemp;
QImage *imageTemp = new QImage();
int X_Start=visibleRect().topLeft().x()/256;
int X_Num=qCeil((float)visibleRect().bottomRight().x()/256.0f-(float)visibleRect().topLeft().x()/256.0f);
int Y_Start=visibleRect().topLeft().y()/256;
int Y_Num=qCeil((float)visibleRect().bottomRight().y()/256.0f-(float)visibleRect().topLeft().y()/256.0f);
LastCenterPoint->setX(visibleRect().center().x());
LastCenterPoint->setY(visibleRect().center().y());
X_Start=(X_Start-X_MAP_MARGIN)>0?(X_Start-X_MAP_MARGIN):0;
Y_Start=(Y_Start-Y_MAP_MARGIN)>0?(Y_Start-Y_MAP_MARGIN):0;
X_Num+=X_MAP_MARGIN;
Y_Num+=Y_MAP_MARGIN;
qDebug()<<"XS:"<<X_Start<<" Num:"<<X_Num;
qDebug()<<"YS:"<<Y_Start<<" Num:"<<Y_Num;
for(int x=X_Start;x<=X_Start+X_Num;x++){
for(int y=Y_Start;y<=Y_Start+Y_Num;y++){
if(Setting->value("MapType",gis::Hybrid).toInt()==gis::Hybrid) TilePathTemp=Setting->value("MapPath","/Users/M410/Documents/Map").toString()+"/Hybrid/gh_"+QString::number(x)+"_"+QString::number(y)+"_"+QString::number(ZoomLevel)+".jpeg" ;
else if(Setting->value("MapType",gis::Sattelite).toInt()==gis::Sattelite) TilePathTemp=Setting->value("MapPath","/Users/M410/Documents/Map").toString()+"/Sattelite/gs_"+QString::number(x)+"_"+QString::number(y)+"_"+QString::number(ZoomLevel)+".jpeg" ;
else if(Setting->value("MapType",gis::Street).toInt()==gis::Street) TilePathTemp=Setting->value("MapPath","/Users/M410/Documents/Map").toString()+"/Street/gm_"+QString::number(x)+"_"+QString::number(y)+"_"+QString::number(ZoomLevel)+".jpeg" ;
QFileInfo check_file(TilePathTemp);
// check if file exists and if yes: Is it really a file and no directory?
if (check_file.exists() && check_file.isFile()) {
// qDebug()<<"Exist!";
imageTemp->load(TilePathTemp);
QPixmap srcImage = QPixmap::fromImage(*imageTemp);
//QPixmap srcImage("qrc:/Map/File1.jpeg");
QGraphicsPixmapItem* item = new QGraphicsPixmapItem(srcImage);
item->setPos(QPointF(x*256, y*256));
m_scene->addItem(item);
// centerOn( width() / 2.0f , height() / 2.0f );
} else {
qDebug()<<"NOT Exist!";
}
}
}
Really, you should consider using QML. The advantage of using QML instead of QGraphicsView is you can iterate a lot faster than if you were working directly in C++. The primary downside is generally increased memory usage and incompatibility with QWidgets.
So if you need unique graphics, and very little "standard widget" stuff, you should use QML first and then QGraphicsView ONLY IF requirements dictate it.
Specific to your project though, Qt has a Map type which could be useful: https://doc.qt.io/qt-5/qml-qtlocation-map.html
I have a grid of buttons, displayed on a stage. Setting and getting the color of the buttons is behaving strangely.
int X=0;
int Y=0;
buttons[X][Y].setColor(Color.BLUE); //this works, the button displays blue
boolean test = (buttons[X][Y].getColor()==Color.BLUE);
System.out.println(test); //prints 'false' , why???
System.out.println(buttons[X][Y].getColor()); //prints '0000ffff'
System.out.println(Color.BLUE); //prints '0000ffff'
I need to be able to set and get the color of the buttons for the game I'm creating. Does anyone know what is going on and what I could do?
The Color objects are different, but they have the same value. So, the objects may not be == equal but will be .equal() equal. See What is the difference between == vs equals() in Java?
This a very simple problem to which I can find no solution:
This is my code:
qint32 pos = ui->twShow->verticalScrollBar()->value();
ui->twShow->blockSignals(true);
//Code for updating the contents QTableWidget twShow, this is done by erasing all cells and adding them again, in case it matters.
ui->twShow->blockSignals(false);
if (pos > 0){
ui->twShow->verticalScrollBar()->setValue(pos);
}
What I want to accomplish is simply to maintain the vertical scroll position. However the setValue function ignores the value pos (I've checked by printing the value before and after the instruction and both times its cero).
I have also tried:
QScrollBar *bar = ui->twShow->verticalScrollBar();
// Same code as before
ui->twShow->setVerticalScrollBar(bar); //This line crashes de program
However the last line crashes the program (which I've checked by commenting it, and it works fine).
Any advice would be greatly appreciated...
Thank you very much
QTableWidget * tw;
int desiredRow;
// before update
desiredRow = tw->row(tw->itemAt(1,1));
...
// update code
...
tw->scrollToItem( tw->item( desiredRow, 0),
QAbstractItemView::EnsureVisible | QAbstractItemView::PositionAtTop );
QAbstractItemView::EnsureVisible = 0.
The 'or' flag converts the result to an integer which is not allowed as parameter of the scrollToItem method. On the other hand enums are not intended to be used as combined flags.
i want to set my font as bold in particular row column position of my tablewidget.
I did like this but getting break.
QFont font("Helvetica", 12, QFont::Bold);
overviewTable->item(2,2)->setFont(font);
Please Help
I think everything is ok. Here what docs said:
void QTableWidgetItem::setFont ( const QFont & font )
Sets the font used to display the item's text to the given font.
Maybe your overviewTable const?
ADDED:
This variant works fine for my Qt 4.6:
tableWidget = new QTableWidget(12, 3, this);
for (int i = 0; i < 12; i++) {
for (int j = 0; j < 3; j++) {
QTableWidgetItem *newItem = new QTableWidgetItem(tr("%1").arg(
(i+1)*(j+1)));
tableWidget->setItem(i, j, newItem);
}
}
QFont font;
font.setBold(true);
tableWidget->item(2, 2)->setFont(font);
Maybe you are getting break because you didn't call setItem() to set an item for the cell (2, 2) before you use overviewTable->item(2,2). As the Qt document says,
QTableWidgetItem * QTableWidget::item(int row, int column) const
Returns the item for the given row and column if one has been set;
otherwise returns 0.
That is, your overviewTable->item(2,2) probably returns 0, thus causes a Segmentation fault in the setFont() call.
So your means to setting font is completely right. You just need to call setItem() at first as mosg's answer suggests.
ADDED:
if your overviewTable is a QTableWidget created in Qt Designer, then in the Designer a double-click on a cell (just to enter its editing mode, no need to actually enter anything) will have the effect of calling setItem() for that cell. Later in your code you can directly using the item() function without having to call setItem() first.