[core] Add color setter function overloads taking stings

These new overloads are intended for use via Python.

This generalizes a pythonization that has been so far localized to
RooFit.

core/base/inc/TAttAxis.h

@@ -14,6 +14,7 @@
 
 #include "Rtypes.h"
 
+class TColorNumber;
 
 class TAttAxis {
 protected:
@@ -62,6 +63,8 @@ class TAttAxis {
    virtual void     SetTitleColor(Color_t color=1);                   // *MENU*
    virtual void     SetTitleFont(Style_t font=62);                    // *MENU*
 
+   void SetLabelColor(TColorNumber lcolor);
+
    ClassDef(TAttAxis,4);  //Axis attributes
 };
 

core/base/inc/TAttFill.h

@@ -15,6 +15,7 @@
 
 #include "Rtypes.h"
 
+class TColorNumber;
 
 class TAttFill {
 
@@ -38,6 +39,8 @@ class TAttFill {
    virtual void     SetFillColorAlpha(Color_t fcolor, Float_t falpha);
    virtual void     SetFillStyle(Style_t fstyle) { fFillStyle = fstyle; } ///< Set the fill area style
 
+   void SetFillColor(TColorNumber);
+
    ClassDef(TAttFill,2)  //Fill area attributes
 };
 

core/base/inc/TAttLine.h

@@ -15,6 +15,8 @@
 
 #include "Rtypes.h"
 
+class TColorNumber;
+
 class TAttLine {
 
 protected:
@@ -42,6 +44,8 @@ class TAttLine {
    virtual void     SetLineStyle(Style_t lstyle) { fLineStyle = lstyle;} ///< Set the line style
    virtual void     SetLineWidth(Width_t lwidth) { fLineWidth = lwidth;} ///< Set the line width
 
+   void SetLineColor(TColorNumber lcolor);
+
    ClassDef(TAttLine,2);  //Line attributes
 };
 

core/base/inc/TAttMarker.h

@@ -15,6 +15,7 @@
 
 #include "Rtypes.h"
 
+class TColorNumber;
 
 class TAttMarker {
 
@@ -47,6 +48,8 @@ class TAttMarker {
    static Style_t GetMarkerStyleBase(Style_t style);
    static Width_t GetMarkerLineWidth(Style_t style);
 
+   void SetMarkerColor(TColorNumber lcolor);
+
    ClassDef(TAttMarker,3);  //Marker attributes
 };
 

core/base/inc/TAttText.h

@@ -15,6 +15,8 @@
 
 #include "Rtypes.h"
 
+class TColorNumber;
+
 class TAttText {
 
 protected:
@@ -47,6 +49,8 @@ class TAttText {
    virtual void     SetTextSize(Float_t tsize=1) { fTextSize = tsize;}     ///< Set the text size
    virtual void     SetTextSizePixels(Int_t npixels);                      ///< Set the text size in pixel
 
+   void SetTextColor(TColorNumber lcolor);
+
    ClassDef(TAttText,2)  //Text attributes
 };
 

core/base/inc/TColor.h

@@ -135,5 +135,16 @@ class TColor : public TNamed {
                        kWaterMelon=108,      kCool=109,        kCopper=110,
                        kGistEarth=111,       kViridis=112,     kCividis=113,
                        kRainbow=kRainBow,    kDarkRainbow=kDarkRainBow};
+
+class TColorNumber {
+public:
+   TColorNumber(Int_t color) : fNumber{color} {}
+   TColorNumber(std::string const &color);
+   Int_t number() const { return fNumber; }
+
+private:
+   Int_t fNumber; ///< Color number identifier
+};
+
 #endif
 

core/base/src/TAttAxis.cxx

@@ -366,3 +366,8 @@ void TAttAxis::Streamer(TBuffer &R__b)
       R__b.WriteClassBuffer(TAttAxis::Class(),this);
    }
 }
+
+void TAttAxis::SetLabelColor(TColorNumber lcolor)
+{
+   SetLabelColor(lcolor.number());
+}

core/base/src/TAttFill.cxx

@@ -267,3 +267,8 @@ void TAttFill::SetFillColorAlpha(Color_t fcolor, Float_t falpha)
 {
    fFillColor = TColor::GetColorTransparent(fcolor, falpha);
 }
+
+void TAttFill::SetFillColor(TColorNumber lcolor)
+{
+   SetFillColor(lcolor.number());
+}

core/base/src/TAttLine.cxx

@@ -306,3 +306,8 @@ void TAttLine::SetLineColorAlpha(Color_t lcolor, Float_t lalpha)
 {
    fLineColor = TColor::GetColorTransparent(lcolor, lalpha);
 }
+
+void TAttLine::SetLineColor(TColorNumber lcolor)
+{
+   SetLineColor(lcolor.number());
+}

core/base/src/TAttMarker.cxx

@@ -379,3 +379,8 @@ void TAttMarker::SetMarkerColorAlpha(Color_t mcolor, Float_t malpha)
 {
    fMarkerColor = TColor::GetColorTransparent(mcolor, malpha);
 }
+
+void TAttMarker::SetMarkerColor(TColorNumber lcolor)
+{
+   SetMarkerColor(lcolor.number());
+}

core/base/src/TAttText.cxx

@@ -432,3 +432,8 @@ void TAttText::SetTextSizePixels(Int_t npixels)
       fTextSize = dy/(pad->GetY2() - pad->GetY1());
    }
 }
+
+void TAttText::SetTextColor(TColorNumber lcolor)
+{
+   SetTextColor(lcolor.number());
+}

core/base/src/TColor.cxx

@@ -20,10 +20,13 @@
 #include "TApplication.h"
 #include "TColorGradient.h"
 #include "snprintf.h"
+
 #include <algorithm>
 #include <cmath>
-#include <iostream>
 #include <fstream>
+#include <iostream>
+#include <sstream>
+#include <stdexcept>
 
 ClassImp(TColor);
 
@@ -2424,7 +2427,7 @@ void TColor::ListColors(Int_t ci, Int_t nb, Bool_t showEmpty)
    printf("   +------+-------+-------+-------+-------+--------------------+--------------------+\n");
    printf("   | Number of possible colors = %4d                                               |\n",ncolors);
    printf("   | Number of defined colors between %4d and %4d = %4d                          |\n",ci,last,nc);
-   printf("   | Number of free indeces between %4d and %4d   = %4d                          |\n",ci,last,last-ci-nc);
+   printf("   | Number of free indices between %4d and %4d   = %4d                          |\n",ci,last,last-ci-nc);
    printf("   +--------------------------------------------------------------------------------+\n\n");
 
 }
@@ -3642,3 +3645,39 @@ void TColor::InvertPalette()
 {
    std::reverse(fgPalette.fArray, fgPalette.fArray + fgPalette.GetSize());
 }
+
+/// The `color` string argument argument will be evaluated
+/// to get the actual ROOT color number, like `kRed`.
+/// Here is how the string is parsed:
+///
+///   1. Match against single-character color codes following the matplotlib convention.
+///      For example, to get red color (equivalent to `kRed`):
+///      ~~~ {.cxx}
+///      hist.SetLineColor("r")
+///      ~~~
+///   2. Check if the string matches an en existing TColor name (see TColor::GetColorByName()).
+///      For example:
+///      ~~~ {.cxx}
+///      hist.SetLineColor("kRed+1")
+///      ~~~
+///
+/// In case no corresponding color is found, a `std::invalid_argument` exception is thrown.
+TColorNumber::TColorNumber(std::string const &color)
+{
+   using Map = std::unordered_map<std::string, Int_t>;
+   // Color dictionary to define matplotlib conventions
+   static Map colorMap{{"r", kRed},   {"b", kBlue},  {"g", kGreen},   {"y", kYellow},
+                       {"w", kWhite}, {"k", kBlack}, {"m", kMagenta}, {"c", kCyan}};
+   auto found = colorMap.find(color);
+   if (found != colorMap.end()) {
+      fNumber = found->second;
+      return;
+   }
+
+   fNumber = TColor::GetColorByName(color.c_str());
+   if (fNumber == -1) {
+      std::stringstream msg;
+      msg << "\"" << color << "\" is not a valid color name";
+      throw std::invalid_argument(msg.str());
+   }
+}

graf2d/gpad/inc/TRatioPlot.h

@@ -27,6 +27,7 @@
 
 #include "TFitResultPtr.h"
 
+class TColorNumber;
 class TH1;
 class TPad;
 class TVirtualPad;
@@ -242,6 +243,7 @@ class TRatioPlot : public TObject {
    virtual void SetGridlines(std::vector<double> gridlines);
 
    void SetConfidenceIntervalColors(Color_t ci1 = kYellow, Color_t ci2 = kGreen);
+   void SetConfidenceIntervalColors(TColorNumber ci1, TColorNumber ci2);
 
    void SetC1(Double_t c1) { fC1 = c1; }
    void SetC2(Double_t c2) { fC2 = c2; }

graf2d/gpad/src/TRatioPlot.cxx

@@ -10,6 +10,7 @@
  *************************************************************************/
 
 #include "TRatioPlot.h"
+#include "TColor.h"
 #include "TROOT.h"
 #include "TBrowser.h"
 #include "TH1.h"
@@ -1703,6 +1704,16 @@ void TRatioPlot::SetConfidenceIntervalColors(Color_t ci1, Color_t ci2)
    fCi2Color = ci2;
 }
 
+
+////////////////////////////////////////////////////////////////////////////////
+/// Set the confidence interval colors.
+
+void TRatioPlot::SetConfidenceIntervalColors(TColorNumber ci1, TColorNumber ci2)
+{
+   fCi1Color = ci1.number();
+   fCi2Color = ci2.number();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 /// Internal method to import TAxis attributes to a TGaxis. Copied from
 /// `TGaxis::ImportAxisAttributes`

graf2d/graf/inc/TGaxis.h

@@ -16,6 +16,8 @@
 #include "TAttText.h"
 #include "TString.h"
 
+
+class TColorNumber;
 class TF1;
 class TAxis;
 class TLatex;
@@ -133,6 +135,8 @@ class TGaxis : public TLine, public TAttText {
    void                SetWmax(Double_t wmax) {fWmax = wmax;}
    static void         SetExponentOffset(Float_t xoff=0., Float_t yoff=0., Option_t *axis="xy");
 
+   void SetLabelColor(TColorNumber lcolor);
+
    ClassDefOverride(TGaxis,6)  //Graphics axis
 };
 

graf2d/graf/src/TGaxis.cxx

@@ -3080,3 +3080,8 @@ void TGaxis::Streamer(TBuffer &R__b)
       R__b.WriteClassBuffer(TGaxis::Class(),this);
    }
 }
+
+void TGaxis::SetLabelColor(TColorNumber lcolor)
+{
+   SetLineColor(lcolor.number());
+}

roofit/roofitcore/inc/RooGlobalFunc.h

@@ -21,6 +21,7 @@
 #include "RooArgSet.h"
 
 #include "ROOT/RConfig.hxx"
+#include <TColor.h>
 
 #include <map>
 #include <string>
@@ -43,6 +44,7 @@ class RooConstVar ;
 class RooRealVar ;
 class RooAbsCategory ;
 class RooNumIntConfig ;
+
 class TH1 ;
 class TTree ;
 
@@ -102,13 +104,11 @@ RooCmdArg Range(const char* rangeName, bool adjustNorm=true) ;
 RooCmdArg Range(double lo, double hi, bool adjustNorm=true) ;
 RooCmdArg NormRange(const char* rangeNameList) ;
 RooCmdArg VLines() ;
-RooCmdArg LineColor(Color_t color) ;
-RooCmdArg LineColor(std::string const &color) ;
+RooCmdArg LineColor(TColorNumber color) ;
 RooCmdArg LineStyle(Style_t style) ;
 RooCmdArg LineStyle(std::string const &style) ;
 RooCmdArg LineWidth(Width_t width) ;
-RooCmdArg FillColor(Color_t color) ;
-RooCmdArg FillColor(std::string const &color) ;
+RooCmdArg FillColor(TColorNumber color) ;
 RooCmdArg FillStyle(Style_t style) ;
 RooCmdArg FillStyle(std::string const &style) ;
 RooCmdArg ProjectionRange(const char* rangeName) ;
@@ -141,8 +141,7 @@ RooCmdArg Binning(int nBins, double xlo=0.0, double xhi=0.0) ;
 RooCmdArg MarkerStyle(Style_t style) ;
 RooCmdArg MarkerStyle(std::string const &style) ;
 RooCmdArg MarkerSize(Size_t size) ;
-RooCmdArg MarkerColor(Color_t color) ;
-RooCmdArg MarkerColor(std::string const &color) ;
+RooCmdArg MarkerColor(TColorNumber color) ;
 RooCmdArg CutRange(const char* rangeName) ;
 RooCmdArg XErrorSize(double width) ;
 RooCmdArg RefreshNorm() ;
@@ -407,7 +406,7 @@ RooCmdArg BaseClassName(const char* name) ;
 RooCmdArg TagName(const char* name) ;
 RooCmdArg OutputStream(std::ostream& os) ;
 RooCmdArg Prefix(bool flag) ;
-RooCmdArg Color(Color_t color) ;
+RooCmdArg Color(TColorNumber color) ;
 
 // RooWorkspace::import() arguments
 RooCmdArg RenameConflictNodes(const char* suffix, bool renameOrigNodes=false) ;