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NAME
- ScaleGadgetRectA
-
scale a gadget rectangle to multiples of font grid boxes
SYNOPSIS
ok = ScaleGadgetRectA(newgadget,tags)
LONG ScaleGadgetRectA(APTR,struct NewGadget *ng,struct TagItem *tags);
LONG ScaleGadgetRectA(APTR,struct NewGadget *ng,...);
A0 A1
LONG ScaleGadgetRectA(APTR,struct NewGadget *ng,...);
FUNCTION
ScaleGadgetRectA() checks the NG_GRIDLAYOUT flag in the NewGadget structure and, if set, performs a font-sensitive scaling of gadget coordinates where the font used for scaling has been defined by SetDesignFontA(). This should best be identical to the font in ng->ng_TextAttr. The upper 12 bits of the gadget positions define multiples of the font width or height divided by four, the lower 4 bits a signed pixel offset (i.e. 0 is no offset, 15 is -1, and 7 is +7, the largest positive offset). After scaling has been performed, NG_GRIDLAYOUT is cleared. This function is also used internally by GadTools for computing the size and position of all gadgets created by CreateGadgetA(), but is present here to pre-compute dimensions, e.g. the size of a window to be opened.
INPUTS
- ng
-
pointer to a NewGadget structure that is to be scaled.
- tags
-
additional tags for setting the design font.
TAGS
- GTVI_AlignRight:
-
Align the right edge of the scaled box to a font grid position rather than scaling the width by the cell width.
- GTVI_AlignBottom:
-
Align the bottom edge of the scaled box to a font grid position rather than scaling the height by the cell height.
RESULT
- ok
-
set if scaling has been performed, 0 if ng remained untouched.
EXAMPLE
The following code computes the pixel coordinates of
1x1 font cell at position 2,3:
ng.ng_LeftEdge = 2 << 6;
ng.ng_TopEdge = 3 << 6;
ng.ng_Width = 1 << 6;
ng.ng_Height = 1 << 6;
ng.ng_Flags = NG_GRIDLAYOUT;
ScaleGadgetRect(&ng,TAG_DONE);
The lower 4 bits are pixel offsets we do not need,
the next 2 bits are fractional font cell locations,
the bits from 6 bit up are integer font cell sizes.
Thus, integer cell positions are upshifted by 6 bits.
As a general rule of thumb, typical buttons are 7 << 4
positions high, i.e. 1.75 cell positions high, and
checkbox gadgets are 6 << 4, i.e. 1.5 font cells high
and 13 << 4, i.e. 12.25 cell positions wide.
Horizontal sliders should be 5 << 4, i.e. 1.25 cell
positions high.
1x1 font cell at position 2,3:
ng.ng_LeftEdge = 2 << 6;
ng.ng_TopEdge = 3 << 6;
ng.ng_Width = 1 << 6;
ng.ng_Height = 1 << 6;
ng.ng_Flags = NG_GRIDLAYOUT;
ScaleGadgetRect(&ng,TAG_DONE);
The lower 4 bits are pixel offsets we do not need,
the next 2 bits are fractional font cell locations,
the bits from 6 bit up are integer font cell sizes.
Thus, integer cell positions are upshifted by 6 bits.
As a general rule of thumb, typical buttons are 7 << 4
positions high, i.e. 1.75 cell positions high, and
checkbox gadgets are 6 << 4, i.e. 1.5 font cells high
and 13 << 4, i.e. 12.25 cell positions wide.
Horizontal sliders should be 5 << 4, i.e. 1.25 cell
positions high.