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https://github.com/kolcha/gradientdialog

simple Qt gradient picker dialog
https://github.com/kolcha/gradientdialog

dialog gradient picker qt

Last synced: about 1 month ago
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simple Qt gradient picker dialog

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README 

        
Gradient Picker Dialog

======================



This project includes the Qt gradient picker library itself and a demo application demonstrating how this dialog looks.



Provided dialog was written as a missing part that complements `QColorDialog` for one personal project that unfortunately did not come to life, and just shared as a likely useful component for some other graphics-related project.



Building

--------



Provided code is compatible only with Qt6, Qt5 support has been dropped. It doesn't require any private Qt interfaces, depends on only the Qt Widgets library.

C++17 is required, some Qt stuff was depreceted since 6.6 and should be replaced with C++17 standard functions.



The build is supported and was tested on major systems: Windows, Linux, and macOS.



CMake is used as a build system, so build it as any usual CMake-based project:



```bash

cmake -B build -D CMAKE_BUILD_TYPE=Release .

cmake --build build

```



Adjust the commands given above depending on the environment (like choosing CMake generator or passing a path to Qt for example) or your preferences/needs (debug/release build for example).



By default, both targets are compiled. As result, you will get a static library containing dialog implementation and executable. If you want to build only the library, just specify the target to `cmake build` command:



```bash

cmake --build build --target gradient_dialog

```



But actually, it costs nothing to build a demo application too, because it is only one source file containing just a few lines (~15) of code.



Usage

-----



The primary header you are interested in is `gradient_dialog.h`, it contains all declarations required to start using it. A dialog can be created in the "classic way" as any other Qt dialog (see demo application for example), easy to use static function is also provided for convenience (like other dialogs do). Examples below.



1. the "classic way" - creating and configuring an object:



   ```cpp

   #include "gradient_dialog.h"



   // somewhere in some event handler (actionOpen in this example)

   void MainWindow::on_actionOpen_triggered()

   {

       // create the dialog itself

       GradientDialog* dlg = new GradientDialog(this);

       // create some initial gradient

       QConicalGradient g(0.5, 0.5, 45.0);

       g.setStops({

           {0.00, {170,   0,   0}},  // #aa0000

           {0.20, {  0,  85, 255}},  // #0055ff

           {0.45, {  0, 170,   0}},  // #00aa00

           {0.65, {255, 255,   0}},  // #ffff00

           {1.00, {170,   0,   0}},  // #aa0000

       });

       // init dialog with gradient

       dlg->setGradient(g);

       // show the dialog

       dlg->open();

   }

   ```



2. convenient way using the static function:



   ```cpp

   #include "gradient_dialog.h"



   // somewhere in some event handler (actionOpen in this example)

   void MainWindow::on_actionOpen_triggered()

   {

       // unfortunately there is no such thing like "invalid gradient"

       // so we need some kind of indicator is dialog was accepted

       bool ok = false;

       // create some initial gradient

       QConicalGradient g(0.5, 0.5, 45.0);

       g.setStops({

           {0.00, {170,   0,   0}},  // #aa0000

           {0.20, {  0,  85, 255}},  // #0055ff

           {0.45, {  0, 170,   0}},  // #00aa00

           {0.65, {255, 255,   0}},  // #ffff00

           {1.00, {170,   0,   0}},  // #aa0000

       });

       // create and show gradient dialog

       QGradient res = GradientDialog::getGradient(&ok, g, this);

       if (ok) {

           // dialog was closed with "OK",

           // it is safe to use 'res', it has valid value

       }

   }

   ```



The first option is more flexible. It is asynchronous and allows to subscribe to `gradientChanged()` signal and track gradient changes on the fly (for example for a live preview of customizing component). The second one is for the sake of simplicity (note the similar syntax compared to `QColorDialog::getColor()`) and it is synchronous (i.e. blocking call).



Final notes

-----------



Returned `QGradient` object has a specific option set



```cpp

m_gradient.setCoordinateMode(QGradient::ObjectMode);

```



so, to use it in your code you may need to change this option or adjust your code. Read more about this option in Qt documentation.