Q3RangeControl Class Reference
#include <q3rangecontrol.h>
List of all members.
Detailed Description
The Q3RangeControl class provides an integer value within a range.
Although originally designed for the QScrollBar widget, the Q3RangeControl can also be used in conjunction with other widgets such as QSlider and QSpinBox. Here are the five main concepts in the class:
1
{Current value} The bounded integer that Q3RangeControl maintains. value() returns it, and several functions, including setValue(), set it.
{Minimum} The lowest value that value() can ever return. Returned by minValue() and set by setRange() or one of the constructors.
{Maximum} The highest value that value() can ever return. Returned by maxValue() and set by setRange() or one of the constructors.
{Line step} The smaller of two natural steps that Q3RangeControl provides and typically corresponds to the user pressing an arrow key. The line step is returned by lineStep() and set using setSteps(). The functions addLine() and subtractLine() respectively increment and decrement the current value by lineStep().
{Page step} The larger of two natural steps that Q3RangeControl provides and typically corresponds to the user pressing PageUp or PageDown. The page step is returned by pageStep() and set using setSteps(). The functions addPage() and substractPage() respectively increment and decrement the current value by pageStep().
Unity (1) may be viewed as a third step size. setValue() lets you set the current value to any integer in the allowed range, not just minValue() + n * lineStep() for integer values of n. Some widgets may allow the user to set any value at all; others may just provide multiples of lineStep() or pageStep().
Q3RangeControl provides three virtual functions that are well suited for updating the on-screen representation of range controls and emitting signals: valueChange(), rangeChange() and stepChange().
Q3RangeControl also provides a function called bound() which lets you force arbitrary integers to be within the allowed range of the range control.
We recommend that all widgets that inherit Q3RangeControl provide at least a signal called valueChanged(); many widgets will want to provide addStep(), addPage(), substractStep() and substractPage() as slots.
Note that you must use multiple inheritance if you plan to implement a widget using Q3RangeControl because Q3RangeControl is not derived from QWidget.
Definition at line 38 of file q3rangecontrol.h.
Constructor & Destructor Documentation
| Q3RangeControl::Q3RangeControl |
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| Q3RangeControl::Q3RangeControl |
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int |
minValue, |
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int |
maxValue, |
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int |
lineStep, |
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int |
pageStep, |
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int |
value | |
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Constructs a range control whose value can never be smaller than minValue or greater than maxValue, whose line step size is lineStep and page step size is pageStep and whose value is initially value (which is guaranteed to be in range using bound()).
Definition at line 120 of file q3rangecontrol.cpp.
References bound(), d, line, maxVal, minVal, page, prevVal, and val.
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| Q3RangeControl::~Q3RangeControl |
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[virtual] |
Member Function Documentation
| int Q3RangeControl::value |
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const [inline] |
| void Q3RangeControl::setValue |
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int |
value |
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| void Q3RangeControl::addPage |
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| void Q3RangeControl::subtractPage |
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| void Q3RangeControl::addLine |
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| void Q3RangeControl::subtractLine |
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| int Q3RangeControl::minValue |
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const [inline] |
| int Q3RangeControl::maxValue |
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const [inline] |
| void Q3RangeControl::setRange |
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int |
minValue, |
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int |
maxValue | |
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| void Q3RangeControl::setMinValue |
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int |
minVal |
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| void Q3RangeControl::setMaxValue |
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int |
maxVal |
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| int Q3RangeControl::lineStep |
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const [inline] |
| int Q3RangeControl::pageStep |
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const [inline] |
| void Q3RangeControl::setSteps |
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int |
lineStep, |
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int |
pageStep | |
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| int Q3RangeControl::bound |
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int |
v |
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const |
| int Q3RangeControl::positionFromValue |
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int |
logical_val, |
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int |
span | |
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Converts logical_val to a pixel position. minValue() maps to 0, maxValue() maps to span and other values are distributed evenly in-between.
This function can handle the entire integer range without overflow, providing span is <= 4096.
Calling this method is useful when actually drawing a range control such as a QScrollBar on-screen.
- See also:
- valueFromPosition()
Definition at line 463 of file q3rangecontrol.cpp.
References maxValue(), minValue(), p, and scale().
00464 {
00465 if (span <= 0 || logical_val < minValue() || maxValue() <= minValue())
00466 return 0;
00467 if (logical_val > maxValue())
00468 return span;
00469
00470 uint range = maxValue() - minValue();
00471 uint p = logical_val - minValue();
00472
00473 if (range > (uint)INT_MAX/4096) {
00474 const int scale = 4096*2;
00475 return ((p/scale) * span) / (range/scale);
00476
00477
00478 } else if (range > (uint)span) {
00479 return (2*p*span + range) / (2*range);
00480 } else {
00481 uint div = span / range;
00482 uint mod = span % range;
00483 return p*div + (2*p*mod + range) / (2*range);
00484 }
00485
00486
00487
00488 }
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| int Q3RangeControl::valueFromPosition |
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int |
pos, |
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int |
span | |
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Converts the pixel position pos to a value. 0 maps to minValue(), span maps to maxValue() and other values are distributed evenly in-between.
This function can handle the entire integer range without overflow.
Calling this method is useful if you actually implemented a range control widget such as QScrollBar and want to handle mouse press events. This function then maps screen coordinates to the logical values.
- See also:
- positionFromValue()
Definition at line 507 of file q3rangecontrol.cpp.
References maxValue(), and minValue().
00508 {
00509 if (span <= 0 || pos <= 0)
00510 return minValue();
00511 if (pos >= span)
00512 return maxValue();
00513
00514 uint range = maxValue() - minValue();
00515
00516 if ((uint)span > range)
00517 return minValue() + (2*pos*range + span) / (2*span);
00518 else {
00519 uint div = range / span;
00520 uint mod = range % span;
00521 return minValue() + pos*div + (2*pos*mod + span) / (2*span);
00522 }
00523
00524
00525
00526 }
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| void Q3RangeControl::directSetValue |
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int |
value |
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[protected] |
| int Q3RangeControl::prevValue |
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const [inline, protected] |
Returns the previous value of the range control. "Previous value" means the value before the last change occurred. Setting a new range may affect the value, too, because the value is forced to be inside the specified range. When the range control is initially created, this is the same as value().
prevValue() can be outside the current legal range if a call to setRange() causes the current value to change. For example, if the range was [0, 1000] and the current value is 500, setRange(0, 400) makes value() return 400 and prevValue() return 500.
- See also:
- value() setRange()
Definition at line 90 of file q3rangecontrol.h.
References prevVal.
| void Q3RangeControl::valueChange |
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[protected, virtual] |
| void Q3RangeControl::rangeChange |
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[protected, virtual] |
This virtual function is called whenever the range control's range changes. You can reimplement it if you want to be notified when the range changes. The default implementation does nothing.
Note that this method is called after the range has changed.
- See also:
- setRange(), valueChange(), stepChange()
Definition at line 407 of file q3rangecontrol.cpp.
Referenced by setRange().
| void Q3RangeControl::stepChange |
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[protected, virtual] |
This virtual function is called whenever the range control's line or page step settings change. You can reimplement it if you want to be notified when the step changes. The default implementation does nothing.
Note that this method is called after a step setting has changed.
- See also:
- setSteps(), rangeChange(), valueChange()
Definition at line 423 of file q3rangecontrol.cpp.
Referenced by setSteps().
Member Data Documentation
The documentation for this class was generated from the following files:
Generated on Thu Mar 15 16:15:21 2007 for Qt 4.2 User's Guide by
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