Rendering Multi-line Text
How do I handle multi-line text rendering in SDL2 with SDL_ttf?
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:
#include <SDL.h>
#include <SDL_ttf.h>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
SDL_Surface* RenderMultilineText(
TTF_Font* font, const std::string& text,
SDL_Color color, int lineSpacing = 0) {
// Split the text into lines
std::vector<std::string> lines;
std::istringstream stream(text);
std::string line;
while (std::getline(stream, line)) {
lines.push_back(line);
}
// Render each line
std::vector<SDL_Surface*> lineSurfaces;
int totalHeight = 0;
int maxWidth = 0;
for (const auto& line : lines) {
SDL_Surface* lineSurface =
TTF_RenderUTF8_Blended(
font, line.c_str(), color);
if (!lineSurface) {
std::cout << "Failed to render line: " <<
TTF_GetError() << '\n';
// Clean up previously rendered surfaces
for (auto surface : lineSurfaces) {
SDL_FreeSurface(surface);
}
return nullptr;
}
lineSurfaces.push_back(lineSurface);
totalHeight += lineSurface->h + lineSpacing;
maxWidth = std::max(maxWidth,
lineSurface->w);
}
// Adjust total height for last line's spacing
if (!lineSurfaces.empty()) {
totalHeight -= lineSpacing;
}
// Create the final surface
SDL_Surface* resultSurface =
SDL_CreateRGBSurfaceWithFormat(
0, maxWidth, totalHeight, 32,
lineSurfaces[0]->format->format);
if (!resultSurface) {
std::cout <<
"Failed to create result surface: " <<
SDL_GetError() << '\n';
for (auto surface : lineSurfaces) {
SDL_FreeSurface(surface);
}
return nullptr;
}
// Blit each line onto the final surface
int yPos = 0;
for (auto lineSurface : lineSurfaces) {
SDL_Rect dstRect = {
0, yPos, lineSurface->w, lineSurface->h};
SDL_BlitSurface(lineSurface, nullptr,
resultSurface, &dstRect);
yPos += lineSurface->h + lineSpacing;
SDL_FreeSurface(lineSurface);
}
return resultSurface;
}
int main() {
SDL_Init(SDL_INIT_VIDEO);
TTF_Init();
TTF_Font* font = TTF_OpenFont(
"path/to/font.ttf", 24);
if (!font) {
std::cout << "Failed to load font: " <<
TTF_GetError() << '\n';
return 1;
}
std::string multilineText =
"This is a multi-line text example.\n"
"It demonstrates how to render\n"
"multiple lines using SDL2 and SDL_ttf.";
SDL_Color textColor = {255, 255, 255, 255};
// White
SDL_Surface* textSurface =
RenderMultilineText(font, multilineText,
textColor, 5);
if (textSurface) {
// Use textSurface in your rendering loop
// ...
SDL_FreeSurface(textSurface);
}
TTF_CloseFont(font);
TTF_Quit();
SDL_Quit();
return 0;
}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.
Rendering Text with SDL_ttf
Learn to render and manipulate text in SDL2 applications using the official SDL_ttf extension