some markup.

README.md

@@ -24,8 +24,98 @@ gwbuild -jNN (with NN number of parallel processes, e.g. 4 for quadcore cpu)
 sudo gwbuild -i
 ```
 
+## Structure of AqDiagram
+
+AqDiagram consists of 4 parts:
+- __data__:
+  Library for data manipulation (accumulate, negate, diff, average, floating average, sums for days and months)
+- __draw__:
+  Library for drawing text and simple figures (points, lines, rectangles), current implementation for libcairo).
+- __placement__:
+  Library for placement of objects in a plane.
+- __graph__:
+  Library for drawing graphs using the other libraries.
+
 
 ## Code Examples
 
-https://gitea.aqbanking.de/martin/aqdiagram/src/branch/master/src/lib/aqdiagram/libtest.c
+### Simple Graph with a Single Curve
+
+```
+  AQDG_GRAPH *g;
+  AQDG_GRAPH_DATAPAIR_LIST *dpList;
+  AQDG_DRAW_CONTEXT *dc;
+  AQDG_OBJECT *graphObject;
+
+  g=AQDG_TimeGraph_new("Title", "Subtitle", "Value", "mm", 0);
+
+  /* get data to be shown (insert your function here) */
+  dpList=CREATE_DATA_FOR_GRAPH();
+
+  /* add single curve as line graph */
+  AQDG_TimeGraph_AddCurve(g, "Testdata", AQDG_GRAPH_TYPE_LINE, dpList);
+
+  /* setup ticks for X and Y axis (use auto-calculated upper and lower limit) */
+  AQDG_TimeGraph_SetupTicks(g, 0, 0.0, 0.0);
+
+  /* draw graph as PNG file (here with 800x600 pixels) */
+  dc=AQDG_Draw_ContextCairo_Png_new("/tmp/testgraph.png", 800, 600);
+  graphObject=AQDG_GraphWidget_new(NULL, AQDG_OBJECT_OPTIONS_STRETCHX | AQDG_OBJECT_OPTIONS_STRETCHY, dc);
+  AQDG_Object_SetWidth(graphObject, 800);
+  AQDG_Object_SetHeight(graphObject, 600);
+
+  /* use default pens and fonts */
+  AQDG_GraphWidget_SetupDefaultPens(graphObject);
+  AQDG_GraphWidget_SetupDefaultFonts(graphObject);
+
+  /* finish creating the PNG file */
+  AQDG_GraphWidget_FinishWithGraph(graphObject, g);
+
+  return 0;
+```
+
+
+
+### Graph with a Bar Graph and a Derived Line Curve
+
+```
+  AQDG_GRAPH *g;
+  AQDG_GRAPH_DATAPAIR_LIST *dpList;
+  AQDG_GRAPH_DATAPAIR_LIST *derivedDpList;
+  AQDG_DRAW_CONTEXT *dc;
+  AQDG_OBJECT *graphObject;
+
+  g=AQDG_TimeGraph_new("Title", "Subtitle", "Value", "mm", 0);
+
+  /* get data to be shown (insert your function here) */
+  dpList=CREATE_DATA_FOR_GRAPH();
+
+  /* add first curve as bar graph */
+  AQDG_TimeGraph_AddCurve(g, "Testdata", AQDG_GRAPH_TYPE_BARS, dpList);
+
+  /* use a data modification function on initial data (here: accumulate) */
+  derivedDpList=AQDG_Data_Accumulate(dpList);
+
+  /* add 2nd curve with accumulated data as line graph */
+  AQDG_TimeGraph_AddCurve(g, "Accumulated", AQDG_GRAPH_TYPE_LINE, derivedDpList);
+
+  /* setup ticks for X and Y axis (use auto-calculated upper and lower limit) */
+  AQDG_TimeGraph_SetupTicks(g, 0, 0.0, 0.0);
+
+  /* draw graph as PNG file (here with 800x600 pixels) */
+  dc=AQDG_Draw_ContextCairo_Png_new("/tmp/testgraph.png", 800, 600);
+  graphObject=AQDG_GraphWidget_new(NULL, AQDG_OBJECT_OPTIONS_STRETCHX | AQDG_OBJECT_OPTIONS_STRETCHY, dc);
+  AQDG_Object_SetWidth(graphObject, 800);
+  AQDG_Object_SetHeight(graphObject, 600);
+
+  /* use default pens and fonts */
+  AQDG_GraphWidget_SetupDefaultPens(graphObject);
+  AQDG_GraphWidget_SetupDefaultFonts(graphObject);
+
+  /* finish creating the PNG file */
+  AQDG_GraphWidget_FinishWithGraph(graphObject, g);
+
+  return 0;
+```
+
 

src/lib/aqdiagram/data/diff.c

@@ -84,3 +84,33 @@ double AQDG_Data_GetAbsMinDiffY(const AQDG_GRAPH_DATAPAIR_LIST *dpList)
 
 
 
+AQDG_GRAPH_DATAPAIR_LIST *AQDG_Data_DifferenceY(const AQDG_GRAPH_DATAPAIR_LIST *dpList)
+{
+  if (dpList && AQDG_Graph_DataPair_List_GetCount(dpList)) {
+    AQDG_GRAPH_DATAPAIR_LIST *newList;
+    const AQDG_GRAPH_DATAPAIR *dp;
+
+    newList=AQDG_Graph_DataPair_List_new();
+    dp=AQDG_Graph_DataPair_List_First(dpList);
+    if (dp) {
+      double lastValue;
+
+      lastValue=AQDG_Graph_DataPair_GetValueY(dp);
+      while(dp) {
+	AQDG_GRAPH_DATAPAIR *newDp;
+	double v;
+
+	v=AQDG_Graph_DataPair_GetValueY(dp);
+	newDp=AQDG_Graph_DataPair_dup(dp);
+	AQDG_Graph_DataPair_SetValueY(newDp, v-lastValue);
+	AQDG_Graph_DataPair_List_Add(newDp, newList);
+	lastValue=v;
+	dp=AQDG_Graph_DataPair_List_Next(dp);
+      }
+      return newList;
+    }
+  }
+  return NULL;
+}
+
+

src/lib/aqdiagram/data/diff.h

@@ -20,6 +20,9 @@ extern "C" {
 
 
 AQDG_API double AQDG_Data_GetAbsMinDiffX(const AQDG_GRAPH_DATAPAIR_LIST *dpList);
+AQDG_API double AQDG_Data_GetAbsMinDiffY(const AQDG_GRAPH_DATAPAIR_LIST *dpList);
+
+AQDG_API AQDG_GRAPH_DATAPAIR_LIST *AQDG_Data_DifferenceY(const AQDG_GRAPH_DATAPAIR_LIST *dpList);
 
 
 

src/lib/aqdiagram/draw/README

@@ -1 +0,0 @@
-Previous af_graphics

src/lib/aqdiagram/graph/axis.t2d

@@ -78,7 +78,7 @@
                    vRun+=vStep;                                                                                \n
                  }                                                                                             \n
                  GWEN_Buffer_free(dbuf);                                                                       \n
-                 return ($(struct_prefix)_HasAtLeastNLevelTicks(st, level, level?1:4))?1:0;                    \n
+                 return ($(struct_prefix)_HasAtLeastNLevelTicks(st, level, level?2:4))?1:0;                    \n
                }                                                                                               \n
           </content>
         </inline>
@@ -110,7 +110,7 @@
                    vRun-=vStep;                                                                                \n
                  }                                                                                             \n
                  GWEN_Buffer_free(dbuf);                                                                       \n
-                 return ($(struct_prefix)_HasAtLeastNLevelTicks(st, level, level?1:4))?1:0;                    \n
+                 return ($(struct_prefix)_HasAtLeastNLevelTicks(st, level, level?2:4))?1:0;                    \n
                }                                                                                               \n
           </content>
         </inline>
@@ -181,6 +181,8 @@
                  rv=_genLog10Ticks(st, vStart, v, vMin, vMax, nextLevel, st-&gt;precision);                \n
                  if (rv)                                                                                   \n
 	                 nextLevel++;                                                                            \n
+                 else                                                                                      \n
+                   $(struct_prefix)_RemoveLevelTicks(st, nextLevel);                                       \n
                  v/=2.0;                                                                                   \n
                                                                                                            \n
                  if (nextLevel&gt;=3)                                                                      \n
@@ -189,6 +191,8 @@
                  rv=_genLog10Ticks(st, vStart, v, vMin, vMax, nextLevel, st-&gt;precision);                \n
                  if (rv)                                                                                   \n
 	                 nextLevel++;                                                                            \n
+                 else                                                                                      \n
+                   $(struct_prefix)_RemoveLevelTicks(st, nextLevel);                                       \n
                  v/=5.0;                                                                                   \n
                } /* for */                                                                                 \n
              }                                                                                             \n