[Interest] QPalette or QLinearGradient does not work on sub widget

[Berkay Elbir]

Finally, I solved it. When I use ui->colorBarWidget->setAutoFillBackground(true)  , all colours are visible. This is default false. In addition, you are right about size. 
Thank you very much.



> On 06 Apr 2016, at 14:54, Berkay Elbir <berkayelbir at gmail.com> wrote:
> 
> Hello,
> 
> Thank you for your answer. But I tried same code, still can not see color. I also fixed the size 
> 
>     ui->colorBarWidget->setFixedSize(71,275);
> 
> I put a button to test my widget is problem or not but it shows button. I do not understand. Is Your designer file different or what is the version of your qt?
> 
> <mainWindow.PNG>
> ​
> 
> 
> My versions are 5.5.1 or 5.6.0
> 
> Thanks,
> 
> Berkay
> 
> On Thu, Mar 31, 2016 at 5:20 PM, Murphy, Sean <smurphy at walbro.com <mailto:smurphy at walbro.com>> wrote:
> Try changing your setBrush line to:
> 
>   palette.setBrush(QPalette::Window, gradient);
> 
> When I do that I get the following:
> 
> <image001.png>
> 
>  
> 
> Also, note that this line
> 
>     QLinearGradient gradient(ui->colorBarWidget->rect().topLeft(),ui->colorBarWidget->rect().topRight());
> 
> Depending on when you call it may not give you the results you’re expecting. If I put your code in my MainWindow constructor I get the picture above. This is because after construction, a resize event happens, so the original gradient calculation was using a different rect width than what the user sees. If you instead create a slot that is connected to a single shot timer like so, you get a gradient that better utilizes the widget’s size.
> 
>  
> 
> #include "mainwindow.h"
> 
> #include "ui_mainwindow.h"
> 
>  
> 
> #include <QPalette>
> 
> #include <QLinearGradient>
> 
>  
> 
> MainWindow::MainWindow(QWidget *parent) :
> 
>     QMainWindow(parent),
> 
>     ui(new Ui::MainWindow)
> 
> {
> 
>     ui->setupUi(this);
> 
>  
> 
>     initTimer = new QTimer(this);
> 
>     connect(initTimer, SIGNAL(timeout()), SLOT(init()));
> 
>     initTimer->setSingleShot(true);
> 
>     initTimer->start(0);
> 
> }
> 
>  
> 
> MainWindow::~MainWindow()
> 
> {
> 
>     delete ui;
> 
> }
> 
>  
> 
> void MainWindow::init()
> 
> {
> 
>     QPalette palette;
> 
>     QLinearGradient gradient(ui->colorBarWidget->rect().topLeft(),ui->colorBarWidget->rect().topRight());
> 
>  
> 
>     gradient.setColorAt(0,   Qt::blue);
> 
>     gradient.setColorAt(0.2, Qt::green);
> 
>     gradient.setColorAt(0.4, Qt::red);
> 
>     gradient.setColorAt(0.6, Qt::yellow);
> 
>     gradient.setColorAt(1,   Qt::cyan);
> 
>     palette.setBrush(QPalette::Window, gradient);
> 
>  
> 
>     ui->colorBarWidget->setPalette(palette);
> 
> }
> 
>  
> 
> <image002.png>
> 
>  
> 
> If you want this gradient to be correct all the time, I think you’ll either need to set that widget to a fixed size, or you’ll have to create your own custom widget and overload resizeEvent(QResizeEvent*) to keep recalculating the gradient when the widget gets resized.
> 
>  
> 
> Sean
> 
>  
> 
> From: Interest [mailto:interest-bounces+smurphy <mailto:interest-bounces%2Bsmurphy>=walbro.com at qt-project.org <mailto:walbro.com at qt-project.org>] On Behalf Of Berkay Elbir
> Sent: Thursday, March 31, 2016 8:19 AM
> To: interest at qt-project.org <mailto:interest at qt-project.org>
> Subject: [Interest] QPalette or QLinearGradient does not work on sub widget
> 
>  
> 
> Hello all,
> 
> I want to ask a question about QPalette and QLinearGradient. 
> 
> I want to brush my sub widget with QLinerGradient. I have created ui by using QtDesigner.
> 
>  <http://i.stack.imgur.com/5JzSK.png>
> But I can not brush this widget by using this code.(ui.colorBarWidget is normal QWidget was created by QtDesigner.)
> 
>    QPalette palette;
>    QLinearGradient gradient(ui.colorBarWidget->rect().topLeft(),ui.colorBarWidget->rect().topRight());
>  
>    gradient.setColorAt(0,   Qt::blue);
>    gradient.setColorAt(0.2, Qt::green);
>    gradient.setColorAt(0.4, Qt::red);
>    gradient.setColorAt(0.6, Qt::yellow);
>    gradient.setColorAt(1,   Qt::cyan);
>    palette.setBrush(QPalette::Base, gradient);
>  
>    ui.colorBarWidget->setPalette(palette);
> In addition this code works in stand alone QWidget application.This is its output:
> 
>  <http://i.stack.imgur.com/z5fc5.png>
> But I can not do same thing in my design. I can do this with styleSheet
> 
> ui.colorBarWidget->setStyleSheet( "background-color: qlineargradient( x1:0 y1:0, x2:0 y2:1, stop:0 blue, stop:1 red )" ); /* works */
> but why I can not do this with QPalette.
> 
> Thanks in advance.
> 
> 
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