cairomm 1.18.0
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A cairo surface represents an image, either as the destination of a drawing operation or as source when drawing onto another surface. More...
#include <cairomm/surface.h>
Public Types | |
enum class | Type { IMAGE = CAIRO_SURFACE_TYPE_IMAGE , PDF = CAIRO_SURFACE_TYPE_PDF , PS = CAIRO_SURFACE_TYPE_PS , XLIB = CAIRO_SURFACE_TYPE_XLIB , XCB = CAIRO_SURFACE_TYPE_XCB , GLITZ = CAIRO_SURFACE_TYPE_GLITZ , QUARTZ = CAIRO_SURFACE_TYPE_QUARTZ , WIN32 = CAIRO_SURFACE_TYPE_WIN32 , WIN32_SURFACE = CAIRO_SURFACE_TYPE_WIN32 , BEOS = CAIRO_SURFACE_TYPE_BEOS , DIRECTFB = CAIRO_SURFACE_TYPE_DIRECTFB , SVG = CAIRO_SURFACE_TYPE_SVG , OS2 = CAIRO_SURFACE_TYPE_OS2 , WIN32_PRINTING = CAIRO_SURFACE_TYPE_WIN32_PRINTING , QUARTZ_IMAGE = CAIRO_SURFACE_TYPE_QUARTZ_IMAGE , SCRIPT = CAIRO_SURFACE_TYPE_SCRIPT , QT = CAIRO_SURFACE_TYPE_QT , RECORDING = CAIRO_SURFACE_TYPE_RECORDING , VG = CAIRO_SURFACE_TYPE_VG , GL = CAIRO_SURFACE_TYPE_GL , DRM = CAIRO_SURFACE_TYPE_DRM , TEE = CAIRO_SURFACE_TYPE_TEE , XML = CAIRO_SURFACE_TYPE_XML , SKIA = CAIRO_SURFACE_TYPE_SKIA , SUBSURFACE = CAIRO_SURFACE_TYPE_SUBSURFACE } |
Cairo::Surface::Type is used to describe the type of a given surface. More... | |
enum class | Format { ARGB32 = CAIRO_FORMAT_ARGB32 , RGB24 = CAIRO_FORMAT_RGB24 , A8 = CAIRO_FORMAT_A8 , A1 = CAIRO_FORMAT_A1 , RGB16_565 = CAIRO_FORMAT_RGB16_565 } |
Cairo::Surface::Format is used to identify the memory format of image data. More... | |
typedef sigc::slot< ErrorStatus(const unsigned char *, unsigned int)> | SlotWriteFunc |
For example: ErrorStatus my_write_func(unsigned char* data, unsigned int length); More... | |
typedef sigc::slot< ErrorStatus(unsigned char *, unsigned int)> | SlotReadFunc |
This is the type of function which is called when a backend needs to read data from an input stream. More... | |
typedef sigc::slot< void()> | SlotDestroy |
For instance, void on_destroy();. More... | |
typedef cairo_surface_t | cobject |
The underlying C cairo surface type. More... | |
Public Member Functions | |
Surface (cairo_surface_t *cobject, bool has_reference=false) | |
Create a C++ wrapper for the C instance. More... | |
Surface (const Surface &)=delete | |
Surface & | operator= (const Surface &)=delete |
virtual | ~Surface () |
const unsigned char * | get_mime_data (const std::string & mime_type, unsigned long & length) |
Return mime data previously attached to surface using the specified mime type. More... | |
void | set_mime_data (const std::string & mime_type, unsigned char *data, unsigned long length, const SlotDestroy & slot_destroy) |
Attach an image in the format mime_type to surface. More... | |
void | unset_mime_data (const std::string & mime_type) |
Remove the data from a surface. More... | |
void | get_font_options (FontOptions & options) const |
Retrieves the default font rendering options for the surface. More... | |
void | finish () |
This function finishes the surface and drops all references to external resources. More... | |
void | flush () |
Do any pending drawing for the surface and also restore any temporary modifications cairo has made to the surface's state. More... | |
void | mark_dirty () |
Tells cairo to consider the data buffer dirty. More... | |
void | mark_dirty (int x, int y, int width, int height) |
Marks a rectangular area of the given surface dirty. More... | |
void | set_device_offset (double x_offset, double y_offset) |
Sets an offset that is added to the device coordinates determined by the CTM when drawing to surface. More... | |
void | get_device_offset (double & x_offset, double & y_offset) const |
Returns a previous device offset set by set_device_offset(). More... | |
void | set_device_scale (double x_scale, double y_scale) |
Sets a scale that is multiplied to the device coordinates determined by the CTM when drawing to surface. More... | |
void | set_device_scale (double scale) |
Sets x and y scale to the same value. More... | |
void | get_device_scale (double & x_scale, double & y_scale) const |
Returns a previous device scale set by set_device_scale(). More... | |
double | get_device_scale () const |
Returns the x and y average of a previous device scale set by set_device_scale(). More... | |
void | set_fallback_resolution (double x_pixels_per_inch, double y_pixels_per_inch) |
Set the horizontal and vertical resolution for image fallbacks. More... | |
void | get_fallback_resolution (double & x_pixels_per_inch, double & y_pixels_per_inch) const |
This function returns the previous fallback resolution set by set_fallback_resolution(), or default fallback resolution if never set. More... | |
Type | get_type () const |
Content | get_content () const |
This function returns the content type of surface which indicates whether the surface contains color and/or alpha information. More... | |
void | copy_page () |
Emits the current page for backends that support multiple pages, but doesn't clear it, so that the contents of the current page will be retained for the next page. More... | |
void | show_page () |
Emits and clears the current page for backends that support multiple pages. More... | |
bool | has_show_text_glyphs () const |
Returns whether the surface supports sophisticated Context::show_text_glyphs() operations. More... | |
void | write_to_png (const std::string & filename) |
Writes the contents of surface to a new file filename as a PNG image. More... | |
void | write_to_png_stream (const SlotWriteFunc & write_func) |
Writes the Surface to the write function. More... | |
RefPtr< Device > | get_device () |
This function returns the device for a surface. More... | |
cobject * | cobj () |
Provides acces to the underlying C cairo surface. More... | |
const cobject * | cobj () const |
Provides acces to the underlying C cairo surface. More... | |
Static Public Member Functions | |
static RefPtr< Surface > | create (const RefPtr< Surface > other, Content content, int width, int height) |
Create a new surface that is as compatible as possible with an existing surface. More... | |
static RefPtr< Surface > | create (const RefPtr< Surface > & target, double x, double y, double width, double height) |
Create a new surface that is a rectangle within the target surface. More... | |
Protected Attributes | |
cobject * | m_cobject |
The underlying C cairo surface type that is wrapped by this Surface. More... | |
A cairo surface represents an image, either as the destination of a drawing operation or as source when drawing onto another surface.
There are different subtypes of cairo surface for different drawing backends. This class is a base class for all subtypes and should not be used directly
Most surface types allow accessing the surface without using Cairo functions. If you do this, keep in mind that it is mandatory that you call Cairo::Surface::flush() before reading from or writing to the surface and that you must use Cairo::Surface::mark_dirty() after modifying it.
Surfaces are reference-counted objects that should be used via Cairo::RefPtr.
typedef cairo_surface_t Cairo::Surface::cobject |
The underlying C cairo surface type.
typedef sigc::slot<void()> Cairo::Surface::SlotDestroy |
For instance, void on_destroy();.
typedef sigc::slot<ErrorStatus(unsigned char* , unsigned int )> Cairo::Surface::SlotReadFunc |
This is the type of function which is called when a backend needs to read data from an input stream.
It is passed the buffer to read the data into and the length of the data in bytes. The read function should return CAIRO_STATUS_SUCCESS if all the data was successfully read, CAIRO_STATUS_READ_ERROR otherwise.
data | the buffer into which to read the data |
length | the amount of data to read |
typedef sigc::slot<ErrorStatus(const unsigned char* , unsigned int )> Cairo::Surface::SlotWriteFunc |
For example: ErrorStatus my_write_func(unsigned char* data, unsigned int length);
This is the type of function which is called when a backend needs to write data to an output stream. It is passed the data to write and the length of the data in bytes. The write function should return CAIRO_STATUS_SUCCESS if all the data was successfully written, CAIRO_STATUS_WRITE_ERROR otherwise.
data | the buffer containing the data to write |
length | the amount of data to write |
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strong |
Cairo::Surface::Format is used to identify the memory format of image data.
New entries may be added in future versions.
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strong |
Cairo::Surface::Type is used to describe the type of a given surface.
The surface types are also known as "backends" or "surface backends" within cairo.
The surface type can be queried with Surface::get_type()
The various Cairo::Surface functions can be used with surfaces of any type, but some backends also provide type-specific functions that must only be called with a surface of the appropriate type.
New entries may be added in future versions.
Enumerator | |
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IMAGE | The surface is of type image. |
The surface is of type pdf. | |
PS | The surface is of type ps. |
XLIB | The surface is of type xlim. |
XCB | The surface is of type xcb. |
GLITZ | The surface is of type glitz. |
QUARTZ | The surface is of type quartz. |
WIN32 | The surface is of type win32.
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WIN32_SURFACE | The surface is of type win32.
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BEOS | The surface is of type beos. |
DIRECTFB | The surface is of type directfb. |
SVG | The surface is of type svg. |
OS2 | The surface is of type os2. |
WIN32_PRINTING | The surface is a win32 printing surface. |
QUARTZ_IMAGE | The surface is of type quartz_image. |
SCRIPT | The surface is of type script.
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QT | The surface is of type Qt.
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RECORDING | The surface is of type recording.
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VG | The surface is a OpenVG surface.
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GL | The surface is of type OpenGL.
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DRM | The surface is of type Direct Render Manager.
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TEE | The surface is of type script 'tee' (a multiplexing surface)
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XML | The surface is of type XML (for debugging)
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SKIA | The surface is of type Skia.
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SUBSURFACE | The surface is of type The surface is a subsurface created with Surface::create()
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explicit |
Create a C++ wrapper for the C instance.
This C++ instance should then be given to a RefPtr.
cobject | The C instance. |
has_reference | Whether we already have a reference. Otherwise, the constructor will take an extra reference. |
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delete |
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virtual |
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inline |
Provides acces to the underlying C cairo surface.
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inline |
Provides acces to the underlying C cairo surface.
void Cairo::Surface::copy_page | ( | ) |
Emits the current page for backends that support multiple pages, but doesn't clear it, so that the contents of the current page will be retained for the next page.
Use show_page() if you want to get an empty page after the emission.
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static |
Create a new surface that is a rectangle within the target surface.
All operations drawn to this surface are then clipped and translated onto the target surface. Nothing drawn via this sub-surface outside of its bounds is drawn onto the target surface, making this a useful method for passing constrained child surfaces to library routines that draw directly onto the parent surface, i.e. with no further backend allocations, double buffering or copies.
@Note The semantics of subsurfaces have not been finalized yet unless the rectangle is in full device units, is contained within the extents of the target surface, and the target or subsurface's device transforms are not changed.
target | an existing surface for which the sub-surface will point to |
x | the x-origin of the sub-surface from the top-left of the target surface (in device-space units) |
y | the y-origin of the sub-surface from the top-left of the target surface (in device-space units) |
width | width of the sub-surface (in device-space units) |
height | height of the sub-surface (in device-space units) |
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static |
Create a new surface that is as compatible as possible with an existing surface.
The new surface will use the same backend as other unless that is not possible for some reason.
other | an existing surface used to select the backend of the new surface |
content | the content for the new surface |
width | width of the new surface, (in device-space units) |
height | height of the new surface (in device-space units) |
void Cairo::Surface::finish | ( | ) |
This function finishes the surface and drops all references to external resources.
For example, for the Xlib backend it means that cairo will no longer access the drawable, which can be freed. After calling finish() the only valid operations on a surface are getting and setting user data and referencing and destroying it. Further drawing to the surface will not affect the surface but will instead trigger a CAIRO_STATUS_SURFACE_FINISHED error.
When the Surface is destroyed, cairo will call finish() if it hasn't been called already, before freeing the resources associated with the Surface.
void Cairo::Surface::flush | ( | ) |
Do any pending drawing for the surface and also restore any temporary modifications cairo has made to the surface's state.
This function must be called before switching from drawing on the surface with cairo to drawing on it directly with native APIs. If the surface doesn't support direct access, then this function does nothing.
Content Cairo::Surface::get_content | ( | ) | const |
This function returns the content type of surface which indicates whether the surface contains color and/or alpha information.
This function returns the device for a surface.
void Cairo::Surface::get_device_offset | ( | double & | x_offset, |
double & | y_offset | ||
) | const |
Returns a previous device offset set by set_device_offset().
double Cairo::Surface::get_device_scale | ( | ) | const |
Returns the x and y average of a previous device scale set by set_device_scale().
void Cairo::Surface::get_device_scale | ( | double & | x_scale, |
double & | y_scale | ||
) | const |
Returns a previous device scale set by set_device_scale().
void Cairo::Surface::get_fallback_resolution | ( | double & | x_pixels_per_inch, |
double & | y_pixels_per_inch | ||
) | const |
This function returns the previous fallback resolution set by set_fallback_resolution(), or default fallback resolution if never set.
x_pixels_per_inch | horizontal pixels per inch |
y_pixels_per_inch | vertical pixels per inch |
void Cairo::Surface::get_font_options | ( | FontOptions & | options | ) | const |
Retrieves the default font rendering options for the surface.
This allows display surfaces to report the correct subpixel order for rendering on them, print surfaces to disable hinting of metrics and so forth. The result can then be used with Cairo::ScaledFont::create().
options | a FontOptions object into which to store the retrieved options. All existing values are overwritten |
const unsigned char * Cairo::Surface::get_mime_data | ( | const std::string & | mime_type, |
unsigned long & | length | ||
) |
Return mime data previously attached to surface using the specified mime type.
If no data has been attached with the given mime type then this returns 0.
mime_type | The MIME type of the image data. |
length | This will be set to the length of the image data. |
Type Cairo::Surface::get_type | ( | ) | const |
bool Cairo::Surface::has_show_text_glyphs | ( | ) | const |
Returns whether the surface supports sophisticated Context::show_text_glyphs() operations.
That is, whether it actually uses the provided text and cluster data to a Context::show_text_glyphs() call.
Note: Even if this function returns FALSE, a Context::show_text_glyphs() operation targeted at this surface will still succeed. It just will act like a Context::show_glyphs() operation. Users can use this function to avoid computing UTF-8 text and cluster mapping if the target surface does not use it.
void Cairo::Surface::mark_dirty | ( | ) |
Tells cairo to consider the data buffer dirty.
In particular, if you've created an ImageSurface with a data buffer that you've allocated yourself and you draw to that data buffer using means other than cairo, you must call mark_dirty() before doing any additional drawing to that surface with cairo.
Note that if you do draw to the Surface outside of cairo, you must call flush() before doing the drawing.
void Cairo::Surface::mark_dirty | ( | int | x, |
int | y, | ||
int | width, | ||
int | height | ||
) |
Marks a rectangular area of the given surface dirty.
x | X coordinate of dirty rectangle |
y | Y coordinate of dirty rectangle |
width | width of dirty rectangle |
height | height of dirty rectangle |
void Cairo::Surface::set_device_offset | ( | double | x_offset, |
double | y_offset | ||
) |
Sets an offset that is added to the device coordinates determined by the CTM when drawing to surface.
One use case for this function is when we want to create a Surface that redirects drawing for a portion of an onscreen surface to an offscreen surface in a way that is completely invisible to the user of the cairo API. Setting a transformation via Cairo::Context::translate() isn't sufficient to do this, since functions like Cairo::Context::device_to_user() will expose the hidden offset.
Note that the offset only affects drawing to the surface, not using the surface in a surface pattern.
x_offset | the offset in the X direction, in device units |
y_offset | the offset in the Y direction, in device units |
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inline |
Sets x and y scale to the same value.
See set_device_scale(double, double) for details.
scale | a scale factor in the X and Y direction |
void Cairo::Surface::set_device_scale | ( | double | x_scale, |
double | y_scale | ||
) |
Sets a scale that is multiplied to the device coordinates determined by the CTM when drawing to surface.
One common use for this is to render to very high resolution display devices at a scale factor, so that code that assumes 1 pixel will be a certain size will still work. Setting a transformation via Cairo::Context::scale() isn't sufficient to do this, since functions like Cairo::Context::device_to_user() will expose the hidden scale.
Note that the scale affects drawing to the surface as well as using the surface in a source pattern.
x_scale | a scale factor in the X direction |
y_scale | a scale factor in the Y direction |
void Cairo::Surface::set_fallback_resolution | ( | double | x_pixels_per_inch, |
double | y_pixels_per_inch | ||
) |
Set the horizontal and vertical resolution for image fallbacks.
When certain operations aren't supported natively by a backend, cairo will fallback by rendering operations to an image and then overlaying that image onto the output. For backends that are natively vector-oriented, this function can be used to set the resolution used for these image fallbacks, (larger values will result in more detailed images, but also larger file sizes).
Some examples of natively vector-oriented backends are the ps, pdf, and svg backends.
For backends that are natively raster-oriented, image fallbacks are still possible, but they are always performed at the native device resolution. So this function has no effect on those backends.
Note: The fallback resolution only takes effect at the time of completing a page (with Context::show_page() or Context::copy_page()) so there is currently no way to have more than one fallback resolution in effect on a single page.
The default fallback resoultion is 300 pixels per inch in both dimensions.
x_pixels_per_inch | Pixels per inch in the x direction |
y_pixels_per_inch | Pixels per inch in the y direction |
void Cairo::Surface::set_mime_data | ( | const std::string & | mime_type, |
unsigned char * | data, | ||
unsigned long | length, | ||
const SlotDestroy & | slot_destroy | ||
) |
Attach an image in the format mime_type to surface.
To remove the data from a surface, call unset_mime_data() with same mime type.
The attached image (or filename) data can later be used by backends which support it (currently: PDF, PS, SVG and Win32 Printing surfaces) to emit this data instead of making a snapshot of the surface. This approach tends to be faster and requires less memory and disk space.
The recognized MIME types are the following: CAIRO_MIME_TYPE_JPEG, CAIRO_MIME_TYPE_PNG, CAIRO_MIME_TYPE_JP2, CAIRO_MIME_TYPE_URI.
See corresponding backend surface docs for details about which MIME types it can handle. Caution: the associated MIME data will be discarded if you draw on the surface afterwards. Use this function with care.
mime_type | The MIME type of the image data. param data The image @data to attach to the surface. param length The length of the image data. |
slot_destroy | A callback slot that will be called when the Surface no longer needs the data. For instance, when the Surface is destroyed or when new image data is attached using the same MIME tpe. |
void Cairo::Surface::show_page | ( | ) |
Emits and clears the current page for backends that support multiple pages.
Use copy_page() if you don't want to clear the page.
void Cairo::Surface::unset_mime_data | ( | const std::string & | mime_type | ) |
Remove the data from a surface.
See set_mime_data().
void Cairo::Surface::write_to_png | ( | const std::string & | filename | ) |
Writes the contents of surface to a new file filename as a PNG image.
filename | the name of a file to write to |
void Cairo::Surface::write_to_png_stream | ( | const SlotWriteFunc & | write_func | ) |
Writes the Surface to the write function.
write_func | The function to be called when the backend needs to write data to an output stream |
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protected |
The underlying C cairo surface type that is wrapped by this Surface.