I'd like to know where exactly is scrollbar buttons' appearance defined?

[newusernew]

For example, in the "default" scheme. How can you tweak their appearance? I know that it's most likely hard-coded somewhere in fltk, ok, then where exactly, what file should I look for?

[Antal Ispanovity]

On Wednesday, April 15, 2020 at 8:41:00 AM UTC+2, newusernew wrote:

For example, in the "default" scheme. How can you tweak their appearance? I know that it's most likely hard-coded somewhere in fltk, ok, then where exactly, what file should I look for?

If I see correctly Fl_Scrollbar.cxx is the widget itself. (Not to be confused with Fl_Scroll). There you can find the draw() method. It draws a horizontal or vertical Fl_Slider and the arrows are drawn with fl_polygon. The arrow style seems to be different for gtk+ scheme. 

[newusernew]

thanks, but I still can't figure out where the slider button up/down boxes are defined.

[Manolo]

On Wednesday, 15 April 2020 10:58:09 UTC+2, newusernew wrote:

thanks, but I still can't figure out where the slider button up/down boxes are defined.

These black triangles are drawn by function Fl_Scrollbar::draw() of file

src/Fl_Scrollbar.cxx by these statements:

    if (Fl::is_scheme("gtk+")) {
      fl_polygon(x1, yy1+w1, x1+w1, yy1+2*w1, x1+w1-1, yy1+w1, x1+w1, yy1);
      x1 += (W-H);
      fl_polygon(x1, yy1, x1+1, yy1+w1, x1, yy1+2*w1, x1+w1, yy1+w1);
    } else {
      fl_polygon(x1, yy1+w1, x1+w1, yy1+2*w1, x1+w1, yy1);
      x1 += (W-H);
      fl_polygon(x1, yy1, x1, yy1+2*w1, x1+w1, yy1+w1);
    }

[newusernew]

I'm not talking about the black triangles, I'm talking about square button shapes that you press, on top of which these black triangles are drawn.

[Antal Ispanovity]

On Wednesday, April 15, 2020 at 12:59:15 PM UTC+2, newusernew wrote:

I'm not talking about the black triangles, I'm talking about square button shapes that you press, on top of which these black triangles are drawn.

Look a couple of lines above the already mentioned code part:

   draw_box((pushed_==1) ? fl_down(slider()) : slider(),

                X, Y, H, H, selection_color());

        draw_box((pushed_==2) ? fl_down(slider()) : slider(),

                X+W-H, Y, H, H, selection_color());

It draws the upper (pused_ == 1) and the lower (pushed_ == 2) box/background. If it's pressed then it draws a "down" version of a box, otherwise the "up" version.

[newusernew]

Antal Ispanovity wrote:

If it's pressed then it draws a "down" version of a box, otherwise the "up" version.

Where does it specify this? 

[imm]

That's what the code Antal showed does; decide which box to draw.

If you have a good look at the code, you'll see it's checking whether pushed is true or not for the slider and hence whether to draw fl_down() or normal...

-- 
Ian
From my Fairphone FP3
   

[Antal Ispanovity]

Let's have a look at this line: 

      draw_box((pushed_==1) ? fl_down(slider()) : slider(),

       X, Y, H, H, selection_color());

Check out the list of box types:

https://www.fltk.org/doc-1.3/common.html#common_boxtypes

and the box drawing function:

https://www.fltk.org/doc-1.3/drawing.html#ssect_Boxes

draw_box is actually Fl_Widget's draw_box but the syntax is the same as fl_draw_box.

If I'm correct buttons are drawn with different style of boxes. For example drawing an FL_UP_BOX looks like a regular button, and FL_DOWN_BOX looks like a button being pressed. the fl_down function (see Enumerations.H) returns with the "pressed" or "down" counterpart of a given box.

The slider() function stores a box style used for drawing the slider.

[newusernew]

Ok, then what part do I have to change in order to replace UP_BOX scrollbar buttons with THIN_UP_BOX buttons, for example?

[Manolo]

On Tuesday, 21 April 2020 01:57:13 UTC+2, newusernew wrote:

Ok, then what part do I have to change in order to replace UP_BOX scrollbar buttons with THIN_UP_BOX buttons, for example?

The slider(Fl_Boxtype) member function of class Fl_Scrollbar inherited from Fl_Slider allows to set the box type

of an Fl_Scrollbar object.

An example, starting from an Fl_Scroll object, would be:

  Fl_Scroll scroll = .....

  scroll.scrollbar.slider(FL_THIN_UP_BOX); // change the boxtype of the vertical scrollbar

  scroll.hscrollbar.slider(FL_ENGRAVED_BOX); // change differently the boxtype of the horizontal scrollbar

[newusernew]

I think I need a solution on a deeper level, that is, I don't want to simply replace boxtypes with other boxtypes, I want to change boxtypes themselves. What do I have to do in order to change the appearance of UP_BOX as such, fundamentally?

[Antal Ispanovity]

On Tuesday, April 21, 2020 at 11:27:59 PM UTC+2, newusernew wrote:

I think I need a solution on a deeper level, that is, I don't want to simply replace boxtypes with other boxtypes, I want to change boxtypes themselves. What do I have to do in order to change the appearance of UP_BOX as such, fundamentally?

Have a look at the documentation, it's very useful. You might need this section: https://www.fltk.org/doc-1.3/common.html#common_custom_boxtypes