/**
* Constructs a new Pattern that represents a linear, two color gradient. Drawing with the pattern
* will cause the resulting area to be tiled with the gradient specified by the arguments.
*
* <p>This operation requires the operating system's advanced graphics subsystem which may not be
* available on some platforms.
*
* @param device the device on which to allocate the pattern
* @param x1 the x coordinate of the starting corner of the gradient
* @param y1 the y coordinate of the starting corner of the gradient
* @param x2 the x coordinate of the ending corner of the gradient
* @param y2 the y coordinate of the ending corner of the gradient
* @param color1 the starting color of the gradient
* @param alpha1 the starting alpha value of the gradient
* @param color2 the ending color of the gradient
* @param alpha2 the ending alpha value of the gradient
* @exception IllegalArgumentException
* <ul>
* <li>ERROR_NULL_ARGUMENT - if the device is null and there is no current device, or if
* either color1 or color2 is null
* <li>ERROR_INVALID_ARGUMENT - if either color1 or color2 has been disposed
* </ul>
*
* @exception SWTException
* <ul>
* <li>ERROR_NO_GRAPHICS_LIBRARY - if advanced graphics are not available
* </ul>
*
* @exception SWTError
* <ul>
* <li>ERROR_NO_HANDLES if a handle for the pattern could not be obtained
* </ul>
*
* @see #dispose()
* @since 3.2
*/
public Pattern(
Device device,
float x1,
float y1,
float x2,
float y2,
Color color1,
int alpha1,
Color color2,
int alpha2) {
super(device);
if (color1 == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
if (color1.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
if (color2 == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
if (color2.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
this.device.checkCairo();
handle = Cairo.cairo_pattern_create_linear(x1, y1, x2, y2);
if (handle == 0) SWT.error(SWT.ERROR_NO_HANDLES);
GC.setCairoPatternColor(handle, 0, color1, alpha1);
GC.setCairoPatternColor(handle, 1, color2, alpha2);
Cairo.cairo_pattern_set_extend(handle, Cairo.CAIRO_EXTEND_REPEAT);
init();
}
/**
* Add a stop to the collection of stops defining the color and alpha blending of this SVG style
* linear or radial gradient.
*
* <p>For linear gradients, the stops represent locations along the gradient vector. For radial
* gradients, they represent locations from the focal point (fx,fy) to the edge of the
* outermost/largest circle.
*
* @param color the color to use at that gradient stop
* @param offset a number between 0.0 and 1.0 which indicates the location of the gradient stop.
* For linear gradients, the �offset� attribute represents a location along the gradient
* vector. For radial gradients, it represents a percentage distance from (fx,fy) to the edge
* of the outermost/largest circle
* @param alpha the alpha value of the gradient at this stop location (from 0 to 255)
* @exception IllegalArgumentException
* <ul>
* <li>ERROR_NULL_ARGUMENT - if color is null
* <li>ERROR_INVALID_ARGUMENT - if color has been disposed
* </ul>
*/
public void addStop(Color color, float /*double*/ offset, int alpha) {
GC.setCairoPatternColor(handle, offset, color, alpha);
}