I am calling it in my view like this:
<%= markdown question.body %>
This is what my ApplicationHelper looks like:
module ApplicationHelper
class HTMLwithPygments < Redcarpet::Render::HTML
def block_code(code, language)
Pygments.highlight(code, lexer:language)
end
end
def markdown(text)
renderer = HTMLwithPygments.new(hard_wrap: true)
options = {
autolink: true,
no_intra_emphasis: true,
fenced_code_blocks: true,
lax_html_blocks: true,
strikethrough: true,
superscript: true
}
Redcarpet::Markdown.new(renderer, options).render(text).html_safe
end
end
But, when it encounters tags like this:
<pre class="lang-cpp prettyprint-override">
It doesn't apply the color highlights to that code. Why is that?
P.S. This is generated, for instance, by Stack Overflow by doing this: <!-- language: lang-cpp -->
Edit 1
Or more specifically, it seems that it won't format the <code> tags that are within <pre> tags. Once <code> is not within <pre> it seems to format it fine. How do I remedy that?
Edit 2
The problem seems to be the data that Pygment.rb is acting on. It is HTML, as can be seen in this gist - https://gist.github.com/marcamillion/14fa121cf3557d38c1a8. So what I want to be able to do is to have Pygment properly format the code returned in the body attribute of that object in my gist.
How do I do that?
Edit 3
This is the HTML code that I would like Pygment.rb and Redcarpet to perform syntax highlighting on:
<p>Here is a piece of C++ code that shows some very peculiar performance. For some strange reason, sorting the data miraculously speeds up the code by almost 6x:</p>
<pre class="lang-cpp prettyprint-override"><code>#include <algorithm>
#include <ctime>
#include <iostream>
int main()
{
// Generate data
const unsigned arraySize = 32768;
int data[arraySize];
for (unsigned c = 0; c < arraySize; ++c)
data[c] = std::rand() % 256;
// !!! With this, the next loop runs faster
std::sort(data, data + arraySize);
// Test
clock_t start = clock();
long long sum = 0;
for (unsigned i = 0; i < 100000; ++i)
{
// Primary loop
for (unsigned c = 0; c < arraySize; ++c)
{
if (data[c] >= 128)
sum += data[c];
}
}
double elapsedTime = static_cast<double>(clock() - start) / CLOCKS_PER_SEC;
std::cout << elapsedTime << std::endl;
std::cout << "sum = " << sum << std::endl;
}
</code></pre>
<ul>
<li>Without <code>std::sort(data, data + arraySize);</code>, the code runs in <strong>11.54</strong> seconds.</li>
<li>With the sorted data, the code runs in <strong>1.93</strong> seconds.</li>
</ul>
<hr>
<p>Initially I thought this might be just a language or compiler anomaly. So I tried it in Java:</p>
<pre class="lang-java prettyprint-override"><code>import java.util.Arrays;
import java.util.Random;
public class Main
{
public static void main(String[] args)
{
// Generate data
int arraySize = 32768;
int data[] = new int[arraySize];
Random rnd = new Random(0);
for (int c = 0; c < arraySize; ++c)
data[c] = rnd.nextInt() % 256;
// !!! With this, the next loop runs faster
Arrays.sort(data);
// Test
long start = System.nanoTime();
long sum = 0;
for (int i = 0; i < 100000; ++i)
{
// Primary loop
for (int c = 0; c < arraySize; ++c)
{
if (data[c] >= 128)
sum += data[c];
}
}
System.out.println((System.nanoTime() - start) / 1000000000.0);
System.out.println("sum = " + sum);
}
}
</code></pre>
<p>with a similar but less extreme result.</p>
<hr>
<p>My first thought was that sorting brings the data into cache, but my next thought was how silly that is because the array was just generated.</p>
<p>What is going on? Why is a sorted array faster than an unsorted array? The code is summing up some independent terms, the order should not matter.</p>
You can see the current way that this particular question is being rendered at: http://boso.herokuapp.com
It is the most popular question on that site, the first one that you see. You will notice that the code simply has a grey background and is indented. There is no pretty highlighting like Pygment.rb promises and does on other code snippets (similarly to how @rorra has illustrated in other examples in his answer).
I can't strip out the HTML - because I want to parse it properly (i.e. make sure the spacing, etc. is included properly). The only difference that I want, is to get syntax highlighting on the code represented in the body of the question.
std::sort(data, data + arraySize);, the code runs in 11.54 seconds.'...that code snippet is properly colored and highlighted. What gives? – Mesocratic