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|
Creating a Skia "Hello World!"
==============================
This tutorial will guide you through the steps to create a Hello World Desktop
application in Skia.
Who this tutorial is for:
-------------------------
This will be useful to you if you want to create a window that can receive
events and to which you can draw with Skia.
Step 1: Check out and build Skia
--------------------------------
Follow the instructions for: Linux, Mac OS X or Windows. The framework that we
will be using does not currently support other platforms.
Once you have a working development environment, we can move on to the next step.
Step 2: Build the included HelloSkia Example
--------------------------------------------
We will be using the "SkiaExamples" framework. You can find it in the
experimental/SkiaExamples directory. There is an included HelloWorld example,
and we will start by building it before we go ahead and create our own.
### On Mac OS X
Run `GYP_GENERATORS="ninja" ./gyp_skia`
This will generate a ninja target, and `ninja -C out/Debug SkiaExamples` will create `SkiaExamples.app`
### On Linux:
Run `GYP_GENERATORS="ninja" ./gyp_skia`
Build the SkiaExamples target:
ninja -C out/Release SkiaExamples
The SkiaExamples binary should be in `out/Release/SkiaExamples`
### On Windows
Run `./gyp_skia`
There should be a Visual Studio project `out/gyp/SkiaExamples.vcproj` with
which you can build the SkiaExamples binary.
### Run the SkiaExamples.
You should see a window open displaying rotating text and some geometry.
Step 3: Create your own Sample
------------------------------
Create a file `experimental/SkiaExamples/Tutorial.cpp` within the Skia tree. Copy the following code:
<!--?prettify lang=cc?-->
~~~~
#include "SkExample.h"
#include "SkDevice.h"
class HelloTutorial : public SkExample {
public:
HelloTutorial(SkExampleWindow* window)
: SkExample(window)
{
fName = "Tutorial"; // This is how Skia will find your example.
fWindow->setupBackend(SkExampleWindow::kGPU_DeviceType);
// Another option is the CPU backend: fWindow->setupBackend(kRaster_DeviceType);
}
protected:
void draw(SkCanvas* canvas) override {
// Clear background
canvas->drawColor(SK_ColorWHITE);
SkPaint paint;
// Draw a message with a nice black paint.
paint.setFlags(SkPaint::kAntiAlias_Flag);
paint.setColor(SK_ColorBLACK);
paint.setTextSize(SkIntToScalar(20));
static const char message[] = "Hello World!";
// Translate and draw the text:
canvas->save();
canvas->translate(SkIntToScalar(50), SkIntToScalar(100));
canvas->drawText(message, strlen(message), SkIntToScalar(0), SkIntToScalar(0), paint);
canvas->restore();
// If you ever want to do animation. Use the inval method to trigger a redraw.
this->fWindow->inval(NULL);
}
};
static SkExample* MyFactory(SkExampleWindow* window) {
return new HelloTutorial(window);
}
static SkExample::Registry registry(MyFactory);
~~~~
Step 4: Compile and run SkiaExamples with your Sample
-----------------------------------------------------
Here is what you have to do to compile your example. There will be
functionality to make this easier, but for now, this is what you have to do:
* Open `gyp/experimental.gyp` and look for the `SkiaExamples` target.
* In the 'sources' section of the SkiaExampels target, add
`../experimental/SkiaExamples/Tutorial.cpp` to the list of sources.
* Repeat Step 2 to update our gyp targets and build our example.
* Run the SkiaExamples, specifying the name of our new example:
$> out/Release/SkiaExamples --match Tutorial
Step 5: How to iterate through multiple examples
------------------------------------------------
If you did not specify an example with the `--match` flag, or if your match
string matches more than one example, you can use the *n* key to iterate
through all of the examples registered.
|
