Provide basic TButton support

It is derived class from TPad and can be painted by TPadPainter

Author: linev

changes.md

@@ -8,11 +8,12 @@
 5. Add more interactive features with `TWebCanvas`
 6. 3-dimensional `TTree::Draw()` now produces `TPolyMarker3D` by default
 7. Force MathJax rendering when `\` symbol is found (#243)
-8. Fix - show correct bin index in `TH2` tooltips
-9. Fix - interactive move/resize on touch devices
-10. Fix - correctly handle axis zooming on lego plots
-11. Fix - histogram statistics calculation with negative bins
-12. Base version for ROOT 6.28 release
+8. Support `TButton` class
+9. Fix - show correct bin index in `TH2` tooltips
+10. Fix - interactive move/resize on touch devices
+11. Fix - correctly handle axis zooming on lego plots
+12. Fix - histogram statistics calculation with negative bins
+13. Base version for ROOT 6.28 release
 
 
 ## Changes in 7.2.1

modules/core.mjs

@@ -5,7 +5,7 @@ let version_id = '7.3.0';
 
 /** @summary version date
   * @desc Release date in format day/month/year like '14/04/2022' */
-let version_date = '13/12/2022';
+let version_date = '14/12/2022';
 
 /** @summary version id and date
   * @desc Produced by concatenation of {@link version_id} and {@link version_date}

modules/draw.mjs

@@ -32,6 +32,7 @@ const drawFuncs = { lst: [
    { name: clTCanvas, icon: 'img_canvas', class: () => import('./gpad/TCanvasPainter.mjs').then(h => h.TCanvasPainter), opt: ';grid;gridx;gridy;tick;tickx;ticky;log;logx;logy;logz', expand_item: 'fPrimitives' },
    { name: clTPad, icon: 'img_canvas', class: () => import('./gpad/TPadPainter.mjs').then(h => h.TPadPainter), opt: ';grid;gridx;gridy;tick;tickx;ticky;log;logx;logy;logz', expand_item: 'fPrimitives' },
    { name: 'TSlider', icon: 'img_canvas', class: () => import('./gpad/TPadPainter.mjs').then(h => h.TPadPainter) },
+   { name: 'TButton', icon: 'img_canvas', class: () => import('./gpad/TPadPainter.mjs').then(h => h.TPadPainter) },
    { name: 'TFrame', icon: 'img_frame', draw: () => import('./gpad/TCanvasPainter.mjs').then(h => h.drawTFrame) },
    { name: clTPave, icon: 'img_pavetext', class: () => import('./hist/TPavePainter.mjs').then(h => h.TPavePainter) },
    { name: clTPaveText, sameas: clTPave },

modules/gpad/TPadPainter.mjs

@@ -178,7 +178,8 @@ class TPadPainter extends ObjectPainter {
       if (!this.iscan && pad?.fName) {
          this.this_pad_name = pad.fName.replace(' ', '_'); // avoid empty symbol in pad name
          let regexp = new RegExp('^[A-Za-z][A-Za-z0-9_]*$');
-         if (!regexp.test(this.this_pad_name)) this.this_pad_name = 'jsroot_pad_' + internals.id_counter++;
+         if (!regexp.test(this.this_pad_name) || ((this.this_pad_name == 'button') && (pad._typename == 'TButton')))
+            this.this_pad_name = 'jsroot_pad_' + internals.id_counter++;
       }
       this.painters = []; // complete list of all painters in the pad
       this.has_canvas = true;