source: opengl-game/gui/ui-value.hpp

#ifndef _UI_VALUE_HPP
#define _UI_VALUE_HPP

#include <sstream>
#include <stdint.h>
#include <string>

#include <SDL2/SDL.h>
#include <SDL2/SDL_ttf.h>

#include "ui-element.hpp"

template<class T>
class UIValue : public UIElement {
public:
   UIValue(int x, int y, string label, T& value, TTF_Font* font, uint32_t textColor,
      SDL_Renderer& renderer);
   ~UIValue() override;

   void render(int x, int y) override;

private:
   string label;
   T* value;
   T oldValue;

   TTF_Font* font;
   SDL_Color textColor;

   SDL_Texture* texture;

   void createTexture();
};

template<class T>
UIValue<T>::UIValue(int x, int y, string label, T& value, TTF_Font* font, uint32_t textColor,
      SDL_Renderer& renderer) :
      UIElement(x, y, 0, 0, renderer, nullptr, nullptr, nullptr),
      label(label), value(&value), oldValue(value), font(font), texture(nullptr) {
   this->textColor = {
      static_cast<Uint8>((textColor >> 24) & 0xFF),
      static_cast<Uint8>((textColor >> 16) & 0xFF),
      static_cast<Uint8>((textColor >> 8) & 0xFF),
      static_cast<Uint8>(textColor & 0xFF)
   };

   this->createTexture();
}

template<class T>
UIValue<T>::~UIValue() {
   if (this->texture != nullptr) {
      SDL_DestroyTexture(this->texture);
      this->texture = nullptr;
   }
}

template<class T>
void UIValue<T>::createTexture() {
   // destroy the old texture before re-creating it
   if (this->texture != nullptr) {
      SDL_DestroyTexture(this->texture);
      this->texture = nullptr;
   }

   ostringstream oss;
   oss << label << *this->value;

   string text = oss.str();

   SDL_Surface* surface = TTF_RenderText_Blended(this->font, text.c_str(),
      this->textColor);
   if (surface == nullptr) {
      cout << "Unable to render text surface! SDL_ttf Error: " << TTF_GetError() << endl;
   }

   this->texture = SDL_CreateTextureFromSurface(&this->renderer, surface);
   if (this->texture == nullptr) {
      cout << "Unable to create texture from rendered text! SDL Error: " << SDL_GetError() << endl;
      // SDL_FreeSurface(surface);
   }

   SDL_FreeSurface(surface);

   TTF_SizeText(this->font, text.c_str(), &this->width, &this->height);
}

template<class T>
void UIValue<T>::render(int x, int y) {
   if (this->oldValue != *this->value) {
      this->createTexture();
      this->oldValue = *this->value;
   }

   SDL_Rect rect = {
         this->x + x,
         this->y + y,
         this->width,
         this->height
   };

   SDL_RenderCopy(&this->renderer, this->texture, nullptr, &rect);
}

#endif // _UI_VALUE_HPP