From d796c9dd933ab96ec83b9a634feedd5d32e1ba3f Mon Sep 17 00:00:00 2001 From: Timothy Pearson Date: Tue, 8 Nov 2011 12:31:36 -0600 Subject: Test conversion to TQt3 from Qt3 8c6fc1f8e35fd264dd01c582ca5e7549b32ab731 --- doc/html/tutorial1-09.html | 155 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 155 insertions(+) create mode 100644 doc/html/tutorial1-09.html (limited to 'doc/html/tutorial1-09.html') diff --git a/doc/html/tutorial1-09.html b/doc/html/tutorial1-09.html new file mode 100644 index 000000000..3edac0352 --- /dev/null +++ b/doc/html/tutorial1-09.html @@ -0,0 +1,155 @@ + + + + + +TQt Tutorial - Chapter 9: With Cannon You Can + + + + + + + +

TQt Tutorial - Chapter 9: With Cannon You Can

+ + +

In this example we become graphic by drawing a cute little blue +cannon. Only cannon.cpp differs from the previous chapter. +

t9/lcdrange.h contains the LCDRange +class definition. +
t9/lcdrange.cpp contains the LCDRange +implementation. +
t9/cannon.h contains the CannonField class +definition. +
t9/cannon.cpp contains the CannonField +implementation. +
t9/main.cpp contains MyWidget and main. +

Line-by-line Walkthrough +

t9/cannon.cpp +

+ +

    void CannonField::paintEvent( TQPaintEvent * )
+    {
+        TQPainter p( this );
+

We'll now start to use TQPainter in earnest. We create a painter that +operates on this widget. +

        p.setBrush( blue );
+

When TQPainter fills a rectangle, a circle, or whatever, it fills the +shape using its brush. Here we set it to use a blue brush. (We +could also use a pattern.) +

        p.setPen( NoPen );
+

And the edges of what TQPainter draws are drawn using the pen. Here we +set it to NoPen, meaning that there will be no special edge when we +draw something; the blue brush will go all the way to the edges of +the things we draw. +

        p.translate( 0, rect().bottom() );
+

The TQPainter::translate() function translates the coordinate +system of the TQPainter; i.e., it moves it by an offset. Here we set +the (0, 0) point to the bottom-left corner of the widget. The x and +y directions remain unchanged, i.e., all the y coordinates inside the +widget are now negative (see The Coordinate +System for more information about TQt's coordinate system). +

        p.drawPie( TQRect(-35, -35, 70, 70), 0, 90*16 );
+

The drawPie() function draws a pie shape inside the specified +rectangle using a start angle and an arc length. The angles are +specified in 1/16th of a degree. Zero degrees is at the 3 o'clock +position. The drawing direction is counter-clockwise. Here we draw a +quarter of a circle in the bottom-left corner of the widget. The pie +is filled with blue and has no outline. +

        p.rotate( -ang );
+

The TQPainter::rotate() function rotates the coordinate system of the +TQPainter around the origin. The rotation argument is a float given +in degrees (not given in 1/16th of a degree as above) and clockwise. +Here we rotate the coordinate system ang degrees counter-clockwise. +

        p.drawRect( TQRect(33, -4, 15, 8) );
+

The TQPainter::drawRect() function draws the specified rectangle. Here +we draw the barrel of the cannon. +

It can often be difficult to envision the resulting drawing when the +coordinate system has been transformed (translated, rotated, scaled, or +sheared) as above. +

In this case the coordinate system is first translated and then rotated. +If the rectangle TQRect(33, -4, 15, 8) had been drawn in the translated +coordinate system, it would have looked like this: +

Note that the rectangle is clipped by the border of the CannonField +widget. When we rotate the coordinate system, for instance 60 +degrees, the rectangle will be rotated around (0, 0), which is the +bottom-left corner because we have translated the coordinate system. +The result looks like this: +

We're done, except that we haven't explained why Windows didn't dither +this time. +

+ +

    int main( int argc, char **argv )
+    {
+        TQApplication::setColorSpec( TQApplication::CustomColor );
+        TQApplication a( argc, argv );
+

We tell TQt that we want a different color-allocation strategy for this +program. There is no single correct color-allocation strategy. Because +this program uses an unusual yellow but not many colors, CustomColor is best. There are several other allocation strategies; you can read about them in the TQApplication::setColorSpec() +documentation. +

Mostly you can ignore this, since the default is good. Occasionally +some applications with unusual color use look bad; changing the +allocation strategy often helps then. +

Behavior +

When the slider is operated the angle of the drawn cannon changes +accordingly. +

The Q on the Quit button is now underlined, and Alt+Q does what you +think it does. If you do not know why, you didn't do the exercises in +Chapter 8. +

You may notice that the cannon flickers annoyingly, especially on a +slow machine. We'll fix this in the next chapter. +

(See Compiling for how to create a +makefile and build the application.) +

Exercises +

Set a different pen instead of NoPen. Set a patterned brush. +

Try "Q&uit" or "Qu&it" as button text instead of "&Quit". What +happens? +

You're now ready for Chapter 10. +

[Previous tutorial] +[Next tutorial] +[Main tutorial page] +

+ +

Trademarks +

TQt 3.3.8

+ -- cgit v1.2.1