Trying overlays

Author: frank-at-adacore

courses/fundamentals_of_ada/273_subprogram_contracts.rst

@@ -539,12 +539,12 @@ Quiz
 Given the following expressions, what is their value if they are evaluated in the postcondition
 of the call :ada:`Set_And_Move ('X', 4)`
 
-.. container:: animate 1
+.. container:: overlay 1
 
    .. image:: subprogram_contracts_special_attributes-quiz.svg
       :width: 50%
 
-.. container:: animate 2
+.. container:: overlay 2
 
    .. image:: subprogram_contracts_special_attributes-answer.svg
       :width: 50%

pandoc/beamer_filter.py

@@ -440,6 +440,10 @@ def is_animate(classes):
     return ("container" in classes) and ("animate" in classes)
 
 
+def is_overlay(classes):
+    return ("container" in classes) and ("overlay" in classes)
+
+
 def animate(classes, contents):
     slide_number = 2
     dash = "-"
@@ -468,6 +472,29 @@ def animate(classes, contents):
     return value
 
 
+def overlay(classes, contents):
+    slide_number = 2
+    if len(classes) > 2:
+        requested = classes[2]
+        if len(requested) > 0:
+            slide_number = int(requested)
+    slide_number = str(slide_number)
+
+    first = {
+        "t": "RawBlock",
+        "c": ["latex", "\\begin{onlyenv}<" + slide_number + ">"],
+    }
+    last = {"t": "RawBlock", "c": ["latex", "\\end{onlyenv}"]}
+
+    value = []
+    value.append(first)
+    for c in contents:
+        value.append(c)
+    value.append(last)
+
+    return value
+
+
 ########################
 ## LATEX ENVIRONMENTS ##
 ########################
@@ -836,6 +863,9 @@ def perform_filter(key, value, format, meta):
             if is_animate(classes):
                 return animate(classes, contents)
 
+            if is_overlay(classes):
+                return overlay(classes, contents)
+
             if is_latex_environment(classes):
                 return latex_environment(classes, contents)