Rendering Text with SDL_ttf

Rendering Multi-line Text

How do I handle multi-line text rendering in SDL2 with SDL_ttf?

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Rendering multi-line text in SDL2 with SDL_ttf requires a bit of extra work, as SDL_ttf doesn't have a built-in function for this. We need to split the text into lines, render each line separately, and then combine them onto a single surface. Here's how we can accomplish this:

Split the text into lines
Render each line as a separate surface
Calculate the total height needed for all lines
Create a new surface large enough to hold all lines
Blit each line onto the new surface
Clean up individual line surfaces

Let's implement this step-by-step:

1#include <SDL.h>
2#include <SDL_ttf.h>
3
4#include <iostream>
5#include <sstream>
6#include <string>
7#include <vector>
8
9SDL_Surface* RenderMultilineText(
10  TTF_Font* font, const std::string& text,
11  SDL_Color color, int lineSpacing = 0) {
12  // Split the text into lines
13  std::vector<std::string> lines;
14  std::istringstream stream(text);
15  std::string line;
16  while (std::getline(stream, line)) {
17    lines.push_back(line);
18  }
19
20  // Render each line
21  std::vector<SDL_Surface*> lineSurfaces;
22  int totalHeight = 0;
23  int maxWidth = 0;
24
25  for (const auto& line : lines) {
26    SDL_Surface* lineSurface =
27      TTF_RenderUTF8_Blended(
28        font, line.c_str(), color);
29    if (!lineSurface) {
30      std::cout << "Failed to render line: " <<
31        TTF_GetError() << '\n';
32      // Clean up previously rendered surfaces
33      for (auto surface : lineSurfaces) {
34        SDL_FreeSurface(surface);
35      }
36      return nullptr;
37    }
38    lineSurfaces.push_back(lineSurface);
39    totalHeight += lineSurface->h + lineSpacing;
40    maxWidth = std::max(maxWidth,
41                        lineSurface->w);
42  }
43
44  // Adjust total height for last line's spacing
45  if (!lineSurfaces.empty()) {
46    totalHeight -= lineSpacing;
47  }
48
49  // Create the final surface
50  SDL_Surface* resultSurface =
51    SDL_CreateRGBSurfaceWithFormat(
52      0, maxWidth, totalHeight, 32,
53      lineSurfaces[0]->format->format);
54
55  if (!resultSurface) {
56    std::cout <<
57      "Failed to create result surface: " <<
58      SDL_GetError() << '\n';
59    for (auto surface : lineSurfaces) {
60      SDL_FreeSurface(surface);
61    }
62    return nullptr;
63  }
64
65  // Blit each line onto the final surface
66  int yPos = 0;
67  for (auto lineSurface : lineSurfaces) {
68    SDL_Rect dstRect = {
69      0, yPos, lineSurface->w, lineSurface->h};
70    SDL_BlitSurface(lineSurface, nullptr,
71                    resultSurface, &dstRect);
72    yPos += lineSurface->h + lineSpacing;
73    SDL_FreeSurface(lineSurface);
74  }
75
76  return resultSurface;
77}
78
79int main() {
80  SDL_Init(SDL_INIT_VIDEO);
81  TTF_Init();
82
83  TTF_Font* font = TTF_OpenFont(
84    "path/to/font.ttf", 24);
85  if (!font) {
86    std::cout << "Failed to load font: " <<
87      TTF_GetError() << '\n';
88    return 1;
89  }
90
91  std::string multilineText =
92    "This is a multi-line text example.\n"
93    "It demonstrates how to render\n"
94    "multiple lines using SDL2 and SDL_ttf.";
95
96  SDL_Color textColor = {255, 255, 255, 255};
97  // White
98  SDL_Surface* textSurface =
99    RenderMultilineText(font, multilineText,
100                        textColor, 5);
101
102  if (textSurface) {
103    // Use textSurface in your rendering loop
104    // ...
105
106    SDL_FreeSurface(textSurface);
107  }
108
109  TTF_CloseFont(font);
110  TTF_Quit();
111  SDL_Quit();
112
113  return 0;
114}

This implementation allows you to render multi-line text with custom line spacing. The RenderMultilineText() function takes the font, text, color, and optional line spacing as parameters.

To use this in your Text class from the lesson, you could modify the CreateSurface() method to use RenderMultilineText() instead of TTF_RenderUTF8_Blended(). This would allow your Text objects to handle multi-line text automatically.

Remember to handle newline characters ('\n') in your text input appropriately. In this example, we use std::getline() to split the text into lines, which automatically handles '\n' characters.

By adjusting the lineSpacing parameter, you can control the vertical distance between lines, allowing for more compact or spacious text layouts as needed for your application.

This Question is from the Lesson: