Re: [fltk.general] Can't figure out how coloring works - Forums

What is it that you actually want to do?
Maybe there’s an easier way (because the Fl_Text_ family are pretty heavyweight, and can be complex to use...)

However, as far at styling goes for Fl_Text_Display and hence Fl_Text_Editor, basically the way it works is there are two “text” buffers associated with the output, one of which holds the actual text to be displayed, and the other holds the styling information.

These two buffers have to be maintained at "the same length”, such that each glyph in the text buffer has a corresponding style code in the style buffer.

The style codes are typically just codes used to index into the style table. They set face, size, colour, basically.

So... the usual way to change the style is to have the modify callback re-scan the text (e.g. when new text is typed, say) compute the new style state, update the style buffer and trigger a redraw.

But if you just want to re-style the text, all you need to do is change the content of the style buffer and trigger a redraw, which you can do directly from your button callback or wherever, or even programmatically if that suits.
You don't need to do it via the modify call-back at all, unless you are doing that anyway (e.g. as part of a styling text editor that needs to parse the input text to determine the style info.)

Hmm, there was a thread about this just recently, um... yes, ended up with this, though the preceding discussion is probably more useful!
https://groups.google.com/g/fltkgeneral/c/Lms9GP18Ou0/m/fzH_AmBZAQAJ

The final product will be e regular _expression_ matcher . There will be an input to search for a regular _expression_ and then a button that will trigger a callback that will search for any matches in the text and it will height them. For the beginning I just want to have a button that will highlight the digits (as the original texteditor-with-dynamic-colors example) when I press it. I don't want it to trigger automatically when I modify the text. I suppose the highlight_data function does this work but I'm not able to call it outside a class so I cannot call it from the button callback. Probably I don't know some things about C++ and that's why I can't make it work. I will send you the code I'm having and maybe you can help if you want and you have free time of course.

Code:

#include <FL/Fl.H>
#include <FL/Fl_Button.H>
#include <FL/Fl_Group.H>
#include <FL/Fl_Input.H>
#include <FL/Fl_Text_Editor.H>
#include <FL/Fl_Window.H>

// Custom class to demonstrate a specialized text editor
class MyEditor : public Fl_Text_Editor {
Fl_Text_Buffer *tbuff;      // text buffer
Fl_Text_Buffer *sbuff;      // style buffer

friend void match_cb(Fl_Widget* w, void* e);

// Modify callback handler
void ModifyCallback(int pos,        // position of update
                    int nInserted, // number of inserted chars
                    int nDeleted,   // number of deleted chars
                    int,            // number of restyled chars (unused here)
                    const char*) { // text deleted (unused here)

    // Nothing inserted or deleted?
    if (nInserted == 0 && nDeleted == 0) return;

    // Characters inserted into tbuff?
    //     Insert same number of chars into style buffer..
    //
    if (nInserted > 0) {
      char *style = new char[nInserted + 1]; // temp buffer
      memset(style, 'A', nInserted);          // init style to "A"s
      style[nInserted] = '\0';                // terminate string
      sbuff->insert(pos, style);              // insert "A"s into style buffer
      delete[] style;                         // done with temp buffer..
    }

    // Characters deleted from tbuff?
    //    Delete same number of chars from style buffer..
    //
    if ( nDeleted > 0 ) {
      sbuff->remove(pos, pos + nDeleted);
      return;     // nothing more to do; deleting won't affect our single char coloring
    }

    // Focus on characters inserted
    int start = pos;
    int end    = pos + nInserted;
    //DEBUG fprintf(stderr, "add_modify_callback(): start/end=%d/%d, text='%.*s'\n", start, end, (end-start), tbuff->address(start));

    // SIMPLE EXAMPLE:
    //     Color the digits 0-4 in green, 5-9 in red.
    //
    for ( int i=start; i<end; i++ ) {
      unsigned int c = tbuff->char_at(i);
      if      ( strchr("01234", c) ) sbuff->replace(i, i+1, "B");   // style 'B' (green)
      else if ( strchr("56789", c) ) sbuff->replace(i, i+1, "C");   // style 'C' (red)
      else                           sbuff->replace(i, i+1, "A");   // style 'A' (black)
    }
}

static void ModifyCallback_STATIC(int pos,                 // position of update
                                    int nInserted,           // number of inserted chars
                                    int nDeleted,            // number of deleted chars
                                    int nRestyled,           // number of restyled chars
                                    const char *deletedText, // text deleted
                                    void *cbarg) {           // callback data
    MyEditor *med = (MyEditor*)cbarg;
    med->ModifyCallback(pos, nInserted, nDeleted, nRestyled, deletedText);
}

public:
MyEditor(int X,int Y,int W,int H) : Fl_Text_Editor(X,Y,W,H) {
    // Style table for the respective styles
    static const Fl_Text_Editor::Style_Table_Entry stable[] = {
       // FONT COLOR      FONT FACE   FONT SIZE
       // --------------- ----------- --------------
       { FL_BLACK,       FL_COURIER, 14 }, // A - Black
       { FL_DARK_GREEN, FL_COURIER, 14 }, // B - Green
       { FL_RED,         FL_COURIER, 14 }, // C - Red
    };
    tbuff = new Fl_Text_Buffer();    // text buffer
    sbuff = new Fl_Text_Buffer();    // style buffer
    buffer(tbuff);
    int stable_size = sizeof(stable)/sizeof(stable[0]);
    highlight_data(sbuff, stable, stable_size, 'A', 0, 0);
}

void text(const char* val) {
    tbuff->text(val);
}
};

MyEditor *edit;

void match_cb(Fl_Widget *w, void *data) {
// Code there
}

int main() {
Fl::scheme("gtk+");

// Windows
Fl_Window *win = new Fl_Window(720, 480, "Text Editor With Dynamic Coloring");

// Text buffer
edit = new MyEditor(10, 70, win->w()-20,win->h()-80);
edit->text("In this editor, digits 0-4 are shown in green, 5-9 shown in red.\n"
             "So here's some numbers 0123456789.\n"
             "Coloring is handled automatically by the add_modify_callback().\n"
             "\n"
             "You can type here to test. ");

// Create the group for the input and the button
Fl_Group *group = new Fl_Group(10, 10, 550, 35);
Fl_Input *input = new Fl_Input(10, 10, 400, 35);
Fl_Button *button = new Fl_Button(420, 10, 95, 35, "Search");
button->callback(match_cb);
button->labelsize(25);
group->end();
group->resizable(input); // Set the "input" to be resizable

win->resizable(*edit); // Set the editor to be resizable
win->size_range(300, 400); // Set the default window size
win->show();
return(Fl::run());
}

So yeah I want to make the match_cb callback call the highlight_data function so it changes the color when I press it. Ignore the input widget for now.