From ea318d1431c89e647598c510c4245c6571aa5f46 Mon Sep 17 00:00:00 2001 From: Timothy Pearson Date: Thu, 26 Jan 2012 23:32:43 -0600 Subject: Update to latest tqt3 automated conversion --- doc/html/coordsys.html | 114 ++++++++++++++++++++++++------------------------- 1 file changed, 57 insertions(+), 57 deletions(-) (limited to 'doc/html/coordsys.html') diff --git a/doc/html/coordsys.html b/doc/html/coordsys.html index ff9e4ce8c..1b497fa98 100644 --- a/doc/html/coordsys.html +++ b/doc/html/coordsys.html @@ -33,9 +33,9 @@ body { background: #ffffff; color: black; } -

A paint device in TQt is a drawable 2D -surface. TQWidget, TQPixmap, TQPicture and TQPrinter are all -paint devices. A TQPainter is an object which can draw on such +

A paint device in TQt is a drawable 2D +surface. TQWidget, TQPixmap, TQPicture and TQPrinter are all +paint devices. A TQPainter is an object which can draw on such devices.

The default coordinate system of a paint device has its origin at the top left corner. X increases to the right and Y increases downwards. @@ -51,83 +51,83 @@ added and colors touched up in the illustration): 

     void MyWidget::paintEvent( TQPaintEvent * )
     {
-        TQPainter p( this );
-        p.setPen( darkGray );
-        p.drawRect( 1,2, 5,4 );
-        p.setPen( lightGray );
-        p.drawLine( 9,2, 7,7 );
+        TQPainter p( this );
+        p.setPen( darkGray );
+        p.drawRect( 1,2, 5,4 );
+        p.setPen( lightGray );
+        p.drawLine( 9,2, 7,7 );
     }

Note that all of the pixels drawn by drawRect() are inside the size specified (5*4 pixels). This is different from some toolkits; in TQt the size you specify exactly encompasses the pixels drawn. This -applies to all the relevant functions in TQPainter. +applies to all the relevant functions in TQPainter.

Similarly, the drawLine() call draws both endpoints of the line, not just one.

Here are the classes that relate most closely to the coordinate system:

-
TQPoint +
TQPoint A single 2D point in the coordinate system. Most functions in -TQt that deal with points can accept either a TQPoint argument -or two ints, for example TQPainter::drawPoint(). -
TQSize -A single 2D vector. Internally, TQPoint and TQSize are the same, +TQt that deal with points can accept either a TQPoint argument +or two ints, for example TQPainter::drawPoint(). +
TQSize +A single 2D vector. Internally, TQPoint and TQSize are the same, but a point is not the same as a size, so both classes exist. Again, most functions accept either a TQSize or two ints, for -example TQWidget::resize(). -
TQRect -A 2D rectangle. Most functions accept either a TQRect or four -ints, for example TQWidget::setGeometry(). -
TQRegion +example TQWidget::resize(). +
TQRect +A 2D rectangle. Most functions accept either a TQRect or four +ints, for example TQWidget::setGeometry(). +
TQRegion An arbitrary set of points, including all the normal set -operations, e.g. TQRegion::intersect(), and also a less +operations, e.g. TQRegion::intersect(), and also a less usual function to return a list of rectangles whose union is -equal to the region. TQRegion is used e.g. by TQPainter::setClipRegion(), TQWidget::repaint() and TQPaintEvent::region(). -
TQPainter +equal to the region. TQRegion is used e.g. by TQPainter::setClipRegion(), TQWidget::repaint() and TQPaintEvent::region(). +
TQPainter The class that paints. It can paint on any device with the -same code. There are differences between devices, TQPrinter::newPage() is a good example, but TQPainter works the +same code. There are differences between devices, TQPrinter::newPage() is a good example, but TQPainter works the same way on all devices. -
TQPaintDevice +
TQPaintDevice A device on which TQPainter can paint. There are two internal -devices, both pixel-based, and two external devices, TQPrinter and TQPicture (which records TQPainter commands to a -file or other TQIODevice, and plays them back). Other +devices, both pixel-based, and two external devices, TQPrinter and TQPicture (which records TQPainter commands to a +file or other TQIODevice, and plays them back). Other devices can be defined.

Transformations

-

Although TQt's default coordinate system works as described above, TQPainter also supports arbitrary transformations. +

Although TQt's default coordinate system works as described above, TQPainter also supports arbitrary transformations.

This transformation engine is a three-step pipeline, closely following the model outlined in books such as Foley & Van Dam and the OpenGL Programming Guide. Refer to those for in-depth coverage; here we give just a brief overview and an example. -

The first step uses the world transformation matrix. Use this matrix +

The first step uses the world transformation matrix. Use this matrix to orient and position your objects in your model. TQt provides -methods such as TQPainter::rotate(), TQPainter::scale(), TQPainter::translate() and so on to operate on this matrix. -

TQPainter::save() and TQPainter::restore() save and restore this -matrix. You can also use TQWMatrix objects, TQPainter::worldMatrix() and TQPainter::setWorldMatrix() to store and +methods such as TQPainter::rotate(), TQPainter::scale(), TQPainter::translate() and so on to operate on this matrix. +

TQPainter::save() and TQPainter::restore() save and restore this +matrix. You can also use TQWMatrix objects, TQPainter::worldMatrix() and TQPainter::setWorldMatrix() to store and use named matrices.

The second step uses the window. The window describes the view boundaries in model coordinates. The matrix positions the objects -and TQPainter::setWindow() positions the window, deciding what +and TQPainter::setWindow() positions the window, deciding what coordinates will be visible. (If you have 3D experience, the window is what's usually called projection in 3D.)

The third step uses the viewport. The viewport too, describes the view boundaries, but in device coordinates. The viewport and the windows describe the same rectangle, but in different coordinate systems. -

On-screen, the default is the entire TQWidget or TQPixmap where +

On-screen, the default is the entire TQWidget or TQPixmap where you are drawing, which is usually appropriate. For printing this function is vital, since very few printers can print over the entire physical page.

So each object to be drawn is transformed into model -coordinates using TQPainter::worldMatrix(), then positioned -on the drawing device using TQPainter::window() and -TQPainter::viewport(). +coordinates using TQPainter::worldMatrix(), then positioned +on the drawing device using TQPainter::window() and +TQPainter::viewport().

It is perfectly possible to do without one or two of the stages. If, -for example, your goal is to draw something scaled, then just using TQPainter::scale() makes perfect sense. If your goal is to use a -fixed-size coordinate system, TQPainter::setWindow() is +for example, your goal is to draw something scaled, then just using TQPainter::scale() makes perfect sense. If your goal is to use a +fixed-size coordinate system, TQPainter::setWindow() is ideal. And so on.

Here is a short example that uses all three mechanisms: the function that draws the clock face in the aclock/aclock.cpp example. We @@ -135,71 +135,71 @@ recommend compiling and running the example before you read any further. In particular, try resizing the window to different sizes.

-

    void AnalogClock::drawClock( TQPainter *paint )
+
    void AnalogClock::drawClock( TQPainter *paint )
     {
-        paint->save();
+        paint->save();
 

 
 Firstly, we save the painter's state, so that the calling function
 is guaranteed not to be disturbed by the transformations we're going
 to use.
-
 
        paint->setWindow( -500,-500, 1000,1000 );
+
 
        paint->setWindow( -500,-500, 1000,1000 );
 

 
 We set the model coordinate system we want a 1000*1000 window where
 0,0 is in the middle.
-
 
        TQRect v = paint->viewport();
-        int d = TQMIN( v.width(), v.height() );
+
 
        TQRect v = paint->viewport();
+        int d = TQMIN( v.width(), v.height() );
 

 
 The device may not be square and we want the clock to be, so we find
 its current viewport and compute its shortest side.
-
 
        paint->setViewport( v.left() + (v.width()-d)/2,
-                            v.top() + (v.height()-d)/2, d, d );
+
 
        paint->setViewport( v.left() + (v.width()-d)/2,
+                            v.top() + (v.height()-d)/2, d, d );
 

 
 Then we set a new square viewport, centered in the old one.
 
 We're now done with our view. From this point on, when we draw in a
 1000*1000 area around 0,0, what we draw will show up in the largest
 possible square that'll fit in the output device.
 
 Time to start drawing.
-
 
        TQPointArray pts;
+
 
        TQPointArray pts;
 

 
 pts is just a temporary variable to hold some points.
 
 Next come three drawing blocks, one for the hour hand, one for the
 minute hand and finally one for the clock face itself. First we draw
 the hour hand:
-
 
        paint->save();
-        paint->rotate( 30*(time.hour()%12-3) + time.minute()/2 );
+
 
        paint->save();
+        paint->rotate( 30*(time.hour()%12-3) + time.minute()/2 );
 

 
 We save the painter and then rotate it so that one axis points along
 the hour hand.
 
 
        pts.setPoints( 4, -20,0,  0,-20, 300,0, 0,20 );
-        paint->drawConvexPolygon( pts );
+        paint->drawConvexPolygon( pts );
 

 
 We set pts to a four-point polygon that looks like the hour hand at
 three o'clock, and draw it. Because of the rotation, it's drawn
 pointed in the right direction.
-
 
        paint->restore();
+
 
        paint->restore();
 

 
 We restore the saved painter, undoing the rotation. We could also
 call rotate( -30 ) but that might introduce rounding errors, so it's
 better to use save() and restore(). Next, the minute hand, drawn
 almost the same way:
-
 
        paint->save();
-        paint->rotate( (time.minute()-15)*6 );
+
 
        paint->save();
+        paint->rotate( (time.minute()-15)*6 );
         pts.setPoints( 4, -10,0, 0,-10, 400,0, 0,10 );
-        paint->drawConvexPolygon( pts );
-        paint->restore();
+        paint->drawConvexPolygon( pts );
+        paint->restore();
 

 
 The only differences are how the rotation angle is computed and the
 shape of the polygon.
 
 The last part to be drawn is the clock face itself.
 
 
        for ( int i=0; i<12; i++ ) {
-            paint->drawLine( 440,0, 460,0 );
-            paint->rotate( 30 );
+            paint->drawLine( 440,0, 460,0 );
+            paint->rotate( 30 );
         }
 

 
 Twelve short hour lines at thirty-degree intervals. At the end of
 that, the painter is rotated in a way which isn't very useful, but
 we're done with painting so that doesn't matter.
-
 
        paint->restore();
+
 
        paint->restore();
     }
 

 
 The final line of the function restores the painter, so that the
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