Add 'Semantic of bargraphs' item in FAQ.

docs/index.html

@@ -473,5 +473,5 @@ <h4 class="modal-title" id="keyboardModalLabel">Keyboard Shortcuts</h4>
 
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 MkDocs version : 1.5.3
-Build Date UTC : 2024-11-29 09:58:26.634211+00:00
+Build Date UTC : 2024-12-09 14:05:10.309696+00:00
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docs/manual/faq/index.html

@@ -381,6 +381,10 @@
             <li class="nav-item" data-level="2"><a href="#displaying-labels-with-numbers" class="nav-link">Displaying labels with numbers</a>
               <ul class="nav flex-column">
               </ul>
+            </li>
+            <li class="nav-item" data-level="2"><a href="#semantic-of-bargraphs" class="nav-link">Semantic of bargraphs</a>
+              <ul class="nav flex-column">
+              </ul>
             </li>
               </ul>
             </li>
@@ -540,7 +544,33 @@ <h2 id="control-rate-versus-audio-rate">Control rate versus audio rate</h2>
 <p>Answer: the <a href="https://faustlibraries.grame.fr/libs/basics/#bakr2ar">ba.kr2ar</a> function can be used for that purpose.</p>
 <h2 id="displaying-labels-with-numbers">Displaying labels with numbers</h2>
 <p>Question: <em>Is there a way to force the sliders to show in numerical order respecting tens?</em> </p>
-<p>Answer: Labels can contain variable parts. These are indicated with the sign % followed by the name of a variable. For a detailed explanation of how to use this feature, refer to the <a href="../syntax/#variable-parts-of-a-label">comprehensive documentation</a>.</p></div>
+<p>Answer: Labels can contain variable parts. These are indicated with the sign % followed by the name of a variable. For a detailed explanation of how to use this feature, refer to the <a href="../syntax/#variable-parts-of-a-label">comprehensive documentation</a>.</p>
+<h2 id="semantic-of-bargraphs">Semantic of bargraphs</h2>
+<p>Question: <em>When are  control rate outputs (like hbargraph/vbargraph) calculated every sample ?</em> </p>
+<p>Answer: This depends on the nature of the signal entering the bargraph. If it's a control rate signal, as in <code>process = vslider("foo", 0, 0, 1, 0.01) : vbargraph("bar", 0, 1);</code>, then updating is done at control rate:</p>
+<pre><code class="language-C++">virtual void compute(int count, FAUSTFLOAT** inputs, FAUSTFLOAT** outputs)
+{
+    FAUSTFLOAT* output0 = outputs[0];
+    fVbargraph0 = FAUSTFLOAT(float(fVslider0));
+    float fSlow0 = fVbargraph0;
+    for (int i0 = 0; i0 &lt; count; i0 = i0 + 1) {
+        output0[i0] = FAUSTFLOAT(fSlow0);
+    }
+}
+</code></pre>
+<p>But if the signal is at sample rate, as in <code>process = vslider("foo", 0, 0, 1, 0.01) : si.smooth(0.9) : vbargraph("bar", 0, 1);</code>, the calculation must be at sample rate to be correct (that is to properly update the signal state at each sample), even if all the values are not displayed:</p>
+<pre><code class="language-C++">virtual void compute(int count, FAUSTFLOAT** inputs, FAUSTFLOAT** outputs) 
+{
+    FAUSTFLOAT* output0 = outputs[0];
+    float fSlow0 = fConst0 * float(fVslider0);
+    for (int i0 = 0; i0 &lt; count; i0 = i0 + 1) {
+        fRec0[0] = fSlow0 + fConst1 * fRec0[1];
+        fVbargraph0 = FAUSTFLOAT(fRec0[0]);
+        output0[i0] = FAUSTFLOAT(fVbargraph0);
+        fRec0[1] = fRec0[0];
+    }
+}
+</code></pre></div>
         </div>
     </div>
 

src/manual/faq.md

@@ -246,3 +246,36 @@ Question: *Is there a way to force the sliders to show in numerical order respec
 
 Answer: Labels can contain variable parts. These are indicated with the sign % followed by the name of a variable. For a detailed explanation of how to use this feature, refer to the [comprehensive documentation](syntax.md#variable-parts-of-a-label).
 
+## Semantic of bargraphs
+
+Question: *When are  control rate outputs (like hbargraph/vbargraph) calculated every sample ?* 
+
+Answer: This depends on the nature of the signal entering the bargraph. If it's a control rate signal, as in `process = vslider("foo", 0, 0, 1, 0.01) : vbargraph("bar", 0, 1);`, then updating is done at control rate:
+
+```C++
+virtual void compute(int count, FAUSTFLOAT** inputs, FAUSTFLOAT** outputs)
+{
+    FAUSTFLOAT* output0 = outputs[0];
+    fVbargraph0 = FAUSTFLOAT(float(fVslider0));
+    float fSlow0 = fVbargraph0;
+    for (int i0 = 0; i0 < count; i0 = i0 + 1) {
+        output0[i0] = FAUSTFLOAT(fSlow0);
+    }
+}
+```
+
+But if the signal is at sample rate, as in `process = vslider("foo", 0, 0, 1, 0.01) : si.smooth(0.9) : vbargraph("bar", 0, 1);`, the calculation must be at sample rate to be correct (that is to properly update the signal state at each sample), even if all the values are not displayed:
+
+```C++
+virtual void compute(int count, FAUSTFLOAT** inputs, FAUSTFLOAT** outputs) 
+{
+    FAUSTFLOAT* output0 = outputs[0];
+    float fSlow0 = fConst0 * float(fVslider0);
+    for (int i0 = 0; i0 < count; i0 = i0 + 1) {
+        fRec0[0] = fSlow0 + fConst1 * fRec0[1];
+        fVbargraph0 = FAUSTFLOAT(fRec0[0]);
+        output0[i0] = FAUSTFLOAT(fVbargraph0);
+        fRec0[1] = fRec0[0];
+    }
+}
+```