12 <concept id="GUID-667E7F90-D6C2-55CE-AE60-6C938072FB9C" xml:lang="en"><title>Graphics

    12 <concept id="GUID-667E7F90-D6C2-55CE-AE60-6C938072FB9C" xml:lang="en"><title>Graphics and Drawing Overview</title><shortdesc>This topic provides an introduction to drawing graphics

    13 and Drawing Overview</title><shortdesc>This topic provides an introduction to drawing graphics to the

    13 to the screen. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 screen. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    17 <p>Applications can draw to any <codeph>RDrawableWindow</codeph> —such as

    16 <p>Applications can draw to any <codeph>RDrawableWindow</codeph> —such

    18 an <xref href="GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79.dita"><apiname>RWindow</apiname></xref> —via a graphics device, of type <xref href="GUID-30479BE3-296E-3B4D-914D-B080ABD733E4.dita"><apiname>CWsScreenDevice</apiname></xref>,

    17 as an <xref href="GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79.dita"><apiname>RWindow</apiname></xref> —via a graphics device, of type <xref href="GUID-30479BE3-296E-3B4D-914D-B080ABD733E4.dita"><apiname>CWsScreenDevice</apiname></xref>, and a graphics context, of type <xref href="GUID-0AEE5955-C530-35F1-A904-69183331B294.dita"><apiname>CWindowGc</apiname></xref>. These classes are derived from the <xref href="GUID-B6D4AEE9-5C17-51D9-BBDE-7CCB5218279D.dita">GDI component</xref> classes <xref href="GUID-500FC564-35E9-3B66-A0C2-1269371A2EA0.dita"><apiname>CGraphicsDevice</apiname></xref> and <xref href="GUID-DAD09DCF-3123-38B4-99E9-91FB24B92138.dita"><apiname>CGraphicsContext</apiname></xref>, respectively. This means that general drawing functions can be

    19 and a graphics context, of type <xref href="GUID-0AEE5955-C530-35F1-A904-69183331B294.dita"><apiname>CWindowGc</apiname></xref>. These classes

    18 used for drawing to windows, as well as to other graphics devices.

    20 are derived from the <xref href="GUID-B6D4AEE9-5C17-51D9-BBDE-7CCB5218279D.dita">GDI

    19 The Window Server itself does not provide the facilities to draw graphics

    21 component</xref> classes <xref href="GUID-500FC564-35E9-3B66-A0C2-1269371A2EA0.dita"><apiname>CGraphicsDevice</apiname></xref> and <xref href="GUID-DAD09DCF-3123-38B4-99E9-91FB24B92138.dita"><apiname>CGraphicsContext</apiname></xref>,

    20 to a physical device. <codeph>CWindowGc</codeph> functions are not

    22 respectively. This means that general drawing functions can be used for drawing

    21 passed to the Window Server directly. Rather, they are stored in a

    23 to windows, as well as to other graphics devices. The Window Server itself

    22 buffer maintained by the Window Server Client API. This buffer is

    24 does not provide the facilities to draw graphics to a physical device. <codeph>CWindowGc</codeph> functions

    23 flushed to the Window Server only rarely. By this means the context

    25 are not passed to the Window Server directly. Rather, they are stored in a

    24 switching involved in drawing is minimised, and system performance

    26 buffer maintained by the Window Server Client API. This buffer is flushed

    25 significantly enhanced. </p>

    27 to the Window Server only rarely. By this means the context switching involved

    28 in drawing is minimised, and system performance significantly enhanced. </p>

    30 aspects of graphics operations. Graphics functions are not carried out directly

    27 aspects of graphics operations. Graphics functions are not carried

    31 via a <codeph>CWsScreenDevice</codeph>, however, but via a graphics context

    28 out directly via a <codeph>CWsScreenDevice</codeph>, however, but

    32 with which it is associated. The graphics context class, <codeph>CWindowGc</codeph>,

    29 via a graphics context with which it is associated. The graphics context

    33 provides a rich set of drawing functions, including functions to draw lines,

    30 class, <codeph>CWindowGc</codeph>, provides a rich set of drawing

    34 arcs, polygons, text and bitmaps. </p>

    31 functions, including functions to draw lines, arcs, polygons, text

    35 <p>A graphics context contains a collection of configurable parameters concerned

    32 and bitmaps. </p>

    36 with graphics, such as pen width, pen color, brush color. It is stored in

    33 <p>A graphics context contains a collection of configurable parameters

    37 the server, thus reducing the amount of information that has to be sent with

    34 concerned with graphics, such as pen width, pen color, brush color.

    38 each graphics call. The graphics call simply specifies the graphics context

    35 It is stored in the server, thus reducing the amount of information

    39 it wishes to use, and a single graphics context can be shared between multiple

    36 that has to be sent with each graphics call. The graphics call simply

    40 windows. </p>

    37 specifies the graphics context it wishes to use, and a single graphics

    41 <p>To draw to a graphics context it must be associated with a window. Typically

    38 context can be shared between multiple windows. </p>

    42 a graphics context is created when a session is constructed, and that graphics

    39 <p>To draw to a graphics context it must be associated with a window.

    43 context is shared between several windows in the application. When the window

    40 Typically a graphics context is created when a session is constructed,

    44 needs to use the graphics context it calls <xref href="GUID-0AEE5955-C530-35F1-A904-69183331B294.dita#GUID-0AEE5955-C530-35F1-A904-69183331B294/GUID-1C0F9DF6-23C2-3707-8F2B-0A738467FF0A"><apiname>CWindowGc::Activate()</apiname></xref>.

    41 and that graphics context is shared between several windows in the

    45 If necessary it can change the graphics context's settings. <xref href="GUID-0AEE5955-C530-35F1-A904-69183331B294.dita#GUID-0AEE5955-C530-35F1-A904-69183331B294/GUID-E977DBB2-8547-3AB7-99E3-9D246DA6CF58"><apiname>CWindowGc::Deactivate()</apiname></xref> should

    42 application. When the window needs to use the graphics context it

    46 be called first if the graphics context is currently active upon another window. </p>

    43 calls <xref href="GUID-0AEE5955-C530-35F1-A904-69183331B294.dita#GUID-0AEE5955-C530-35F1-A904-69183331B294/GUID-1C0F9DF6-23C2-3707-8F2B-0A738467FF0A"><apiname>CWindowGc::Activate()</apiname></xref>. If necessary it can

    44 change the graphics context's settings. <xref href="GUID-0AEE5955-C530-35F1-A904-69183331B294.dita#GUID-0AEE5955-C530-35F1-A904-69183331B294/GUID-E977DBB2-8547-3AB7-99E3-9D246DA6CF58"><apiname>CWindowGc::Deactivate()</apiname></xref> should be called first if the graphics context is currently active

    45 upon another window. </p>

    50 <li id="GUID-C8AC84D6-AF17-5975-88B8-CC93C499DFA0"><p>Each window is associated

    49 <li id="GUID-C8AC84D6-AF17-5975-88B8-CC93C499DFA0"><p>Each window

    51 with an <codeph>RWsSession</codeph> which is in turn associated with a client-side

    50 is associated with an <codeph>RWsSession</codeph> which is in turn

    52 buffer. Instead of implementing graphics operations by a direct client-server

    51 associated with a client-side buffer. Instead of implementing graphics

    53 call, which involves expensive context switching, all graphics operations

    52 operations by a direct client-server call, which involves expensive

    54 are stored as opcodes in the buffer, and the buffer is only flushed in certain

    53 context switching, all graphics operations are stored as opcodes in

    55 circumstances. </p> </li>

    54 the buffer, and the buffer is only flushed in certain circumstances. </p> </li>

    56 <li id="GUID-00B3FC8E-25DE-542F-BF67-0F71CF22526A"><p>The <codeph>CFbsBitmap</codeph> class

    55 <li id="GUID-00B3FC8E-25DE-542F-BF67-0F71CF22526A"><p>The <codeph>CFbsBitmap</codeph> class allows a bitmap to be shared between all

    57 allows a bitmap to be shared between all threads in the system, including

    56 threads in the system, including the client and the Window Server.

    58 the client and the Window Server. This sharing is mediated by the <xref href="GUID-A03FB1BF-F67B-519D-A904-74CA3F8375D9.dita">Font

    57 This sharing is mediated by the <xref href="GUID-A03FB1BF-F67B-519D-A904-74CA3F8375D9.dita">Font and Bitmap server</xref>. The <xref href="GUID-17150D76-BB82-3A4B-8B1A-8BA93CB1A9EF.dita"><apiname>CWsBitmap</apiname></xref> class eliminates further context

    59 and Bitmap server</xref>. The <xref href="GUID-17150D76-BB82-3A4B-8B1A-8BA93CB1A9EF.dita"><apiname>CWsBitmap</apiname></xref> class eliminates

    58 switches by taking ownership of the handle of the bitmap. Applications

    60 further context switches by taking ownership of the handle of the bitmap.

    59 can use this class to more efficiently open, blit-to-screen, and close

    61 Applications can use this class to more efficiently open, blit-to-screen,

    60 a series of bitmaps. Use functions that take a <codeph>CWsBitmap</codeph> in preference to those that take a <codeph>CFbsBitmap</codeph>,

    62 and close a series of bitmaps. Use functions that take a <codeph>CWsBitmap</codeph> in

    61 because they are faster. </p> </li>

    63 preference to those that take a <codeph>CFbsBitmap</codeph>, because they

    62 <li id="GUID-550D1374-C166-54C6-A055-0CA040691654"><p>A single graphics

    64 are faster. </p> </li>

    63 context may be used for drawing to many windows—it is not necessary

    65 <li id="GUID-550D1374-C166-54C6-A055-0CA040691654"><p>A single graphics context

    64 to have one per window. The <codeph>Activate()</codeph> function associates

    66 may be used for drawing to many windows—it is not necessary to have one per

    65 a <codeph>CWindowGc</codeph> with a particular window. </p> </li>

    67 window. The <codeph>Activate()</codeph> function associates a <codeph>CWindowGc</codeph> with

    66 <li id="GUID-91AFC884-0BB2-5A73-B757-94EF1B2328A7"><p>Provided drawing

    68 a particular window. </p> </li>

    67 operations to an <xref href="GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79.dita"><apiname>RWindow</apiname></xref> are performed as <xref href="GUID-8DB1C618-597C-560C-95A2-C0AB2CEBB027.dita">redraw drawing</xref>, the Window Server stores the sequence of drawing commands that

    69 <li id="GUID-91AFC884-0BB2-5A73-B757-94EF1B2328A7"><p>Provided drawing operations

    68 represent the window contents in redraw stores. Then when the Window

    70 to an <xref href="GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79.dita"><apiname>RWindow</apiname></xref> are performed as <xref href="GUID-8DB1C618-597C-560C-95A2-C0AB2CEBB027.dita">redraw

    69 Server needs to repaint the window (because, for example, a dialog

    71 drawing</xref>, the Window Server stores the sequence of drawing commands

    70 box popped up over it and has now closed) it simply replays the sequence

    72 that represent the window contents in redraw stores. Then when the Window

    71 of stored commands, rather than sending a redraw request to the client.

    73 Server needs to repaint the window (because, for example, a dialog box popped

    72 This minimizes the number of client-server transactions and means

    74 up over it and has now closed) it simply replays the sequence of stored commands,

    73 that windows are repainted as soon as the Window Server detects that

    75 rather than sending a redraw request to the client. This minimizes the number

    74 they are needed. </p> <p>This means that all <xref href="GUID-0AEE5955-C530-35F1-A904-69183331B294.dita"><apiname>CWindowGc</apiname></xref> drawing should now be redraw drawing, which means that it takes

    76 of client-server transactions and means that windows are repainted as soon

    75 place between <xref href="GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79.dita#GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79/GUID-9337538E-7A53-3153-A330-968B5E4F2FF2"><apiname>RWindow::BeginRedraw()</apiname></xref> and <xref href="GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79.dita#GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79/GUID-3DE16607-AD3B-3946-BEB3-88512EAAB9CE"><apiname>RWindow::EndRedraw()</apiname></xref> calls. If you use the <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-D5458F8C-E199-37DD-B821-050B749122C6"><apiname>CCoeControl::DrawNow()</apiname></xref> and <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-9FB682AC-0209-302A-83F3-7BCB1162B998"><apiname>CCoeControl::DrawDeferred()</apiname></xref> methods, the

    77 as the Window Server detects that they are needed. </p> <p>This means that

    76 UI Control Framework (CONE) takes care of this for you. See <xref href="GUID-8DB1C618-597C-560C-95A2-C0AB2CEBB027.dita">Redraw Drawing</xref> for more information. </p> </li>

    78 all <xref href="GUID-0AEE5955-C530-35F1-A904-69183331B294.dita"><apiname>CWindowGc</apiname></xref> drawing should now be redraw drawing, which

    79 means that it takes place between <xref href="GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79.dita#GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79/GUID-9337538E-7A53-3153-A330-968B5E4F2FF2"><apiname>RWindow::BeginRedraw()</apiname></xref> and <xref href="GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79.dita#GUID-683603DD-F3D3-3193-BEB3-8236C7DE7F79/GUID-3DE16607-AD3B-3946-BEB3-88512EAAB9CE"><apiname>RWindow::EndRedraw()</apiname></xref> calls.

    80 If you use the <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-D5458F8C-E199-37DD-B821-050B749122C6"><apiname>CCoeControl::DrawNow()</apiname></xref> and <xref href="GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160.dita#GUID-B06F99BD-F032-3B87-AB26-5DD6EBE8C160/GUID-9FB682AC-0209-302A-83F3-7BCB1162B998"><apiname>CCoeControl::DrawDeferred()</apiname></xref> methods,

    81 the UI Control Framework (CONE) takes care of this for you. See <xref href="GUID-8DB1C618-597C-560C-95A2-C0AB2CEBB027.dita">Redraw

    82 Drawing</xref> for more information. </p> </li>

    87 <link href="GUID-6C16417B-5B37-5310-B59A-750D971AA6D4.dita"><linktext>The UI Control

    81 <link href="GUID-6C16417B-5B37-5310-B59A-750D971AA6D4.dita"><linktext>The UI Control Framework

    88 Framework (CONE)</linktext></link>

    82 (CONE)</linktext></link>