feat: Improve readability of history and streak charts

References: #432

uhabits-android/src/main/java/org/isoron/uhabits/activities/common/views/HistoryChart.java

@@ -73,14 +73,14 @@ public class HistoryChart extends ScrollableChart
 
     private int colors[];
 
+    private int textColors[];
+
     private RectF baseLocation;
 
     private int primaryColor;
 
     private boolean isBackgroundTransparent;
 
-    private int textColor;
-
     private int reverseTextColor;
 
     private boolean isEditable;
@@ -235,7 +235,7 @@ public class HistoryChart extends ScrollableChart
         headerOverflow = 0;
         previousMonth = "";
         previousYear = "";
-        pTextHeader.setColor(textColor);
+        pTextHeader.setColor(textColors[1]);
 
         updateDate();
         GregorianCalendar currentDate = (GregorianCalendar) baseDate.clone();
@@ -352,6 +352,9 @@ public class HistoryChart extends ScrollableChart
                             GregorianCalendar date,
                             int checkmarkOffset)
     {
+
+        pSquareFg.setColor(textColors[0]);
+
         if (checkmarkOffset >= checkmarks.length) pSquareBg.setColor(colors[0]);
         else
         {
@@ -359,12 +362,15 @@ public class HistoryChart extends ScrollableChart
             if(checkmark == 0) pSquareBg.setColor(colors[0]);
             else if(checkmark < target)
             {
-                pSquareBg.setColor(isNumerical ? textColor : colors[1]);
+                pSquareBg.setColor(isNumerical ? textColors[1] : colors[1]);
+            }
+            else
+            {
+                pSquareBg.setColor(colors[2]);
+                pSquareFg.setColor(textColors[2]);
             }
-            else pSquareBg.setColor(colors[2]);
         }
 
-        pSquareFg.setColor(reverseTextColor);
         canvas.drawRect(location, pSquareBg);
         String text = Integer.toString(date.get(Calendar.DAY_OF_MONTH));
         canvas.drawText(text, location.centerX(),
@@ -411,7 +417,11 @@ public class HistoryChart extends ScrollableChart
             colors[0] = Color.argb(16, 255, 255, 255);
             colors[1] = Color.argb(128, red, green, blue);
             colors[2] = primaryColor;
-            textColor = Color.WHITE;
+
+            textColors = new int[3];
+            textColors[2] = Color.WHITE;
+            textColors[1] = Color.WHITE;
+            textColors[0] = Color.WHITE;
             reverseTextColor = Color.WHITE;
         }
         else
@@ -420,9 +430,13 @@ public class HistoryChart extends ScrollableChart
             colors[0] = res.getColor(R.attr.lowContrastTextColor);
             colors[1] = Color.argb(127, red, green, blue);
             colors[2] = primaryColor;
-            textColor = res.getColor(R.attr.mediumContrastTextColor);
+
-            reverseTextColor =
+            textColors = new int[3];
-                res.getColor(R.attr.highContrastReverseTextColor);
+            textColors[2] = res.getColor(R.attr.highContrastReverseTextColor);
+            textColors[1] = res.getColor(R.attr.mediumContrastTextColor);
+            textColors[0] = res.getColor(R.attr.lowContrastReverseTextColor);
+
+            reverseTextColor = res.getColor(R.attr.highContrastReverseTextColor);
         }
     }
 

uhabits-android/src/main/java/org/isoron/uhabits/activities/common/views/StreakChart.java

@@ -45,6 +45,7 @@ public class StreakChart extends View
     private long maxLength;
 
     private int[] colors;
+    private int[] textColors;
 
     private RectF rect;
 
@@ -70,8 +71,6 @@ public class StreakChart extends View
 
     private int textColor;
 
-    private int reverseTextColor;
-
     public StreakChart(Context context)
     {
         super(context);
@@ -207,7 +206,7 @@ public class StreakChart extends View
 
         float yOffset = rect.centerY() + 0.3f * em;
 
-        paint.setColor(reverseTextColor);
+        paint.setColor(percentageToTextColor(percentage));
         paint.setTextAlign(Paint.Align.CENTER);
         canvas.drawText(Long.toString(streak.getLength()), rect.centerX(),
             yOffset, paint);
@@ -217,7 +216,7 @@ public class StreakChart extends View
             String startLabel = dateFormat.format(streak.getStart().toJavaDate());
             String endLabel = dateFormat.format(streak.getEnd().toJavaDate());
 
-            paint.setColor(textColor);
+            paint.setColor(textColors[1]);
             paint.setTextAlign(Paint.Align.RIGHT);
             canvas.drawText(startLabel, gap - textMargin, yOffset, paint);
 
@@ -252,8 +251,11 @@ public class StreakChart extends View
         colors[2] = Color.argb(192, red, green, blue);
         colors[1] = Color.argb(96, red, green, blue);
         colors[0] = res.getColor(R.attr.lowContrastTextColor);
-        textColor = res.getColor(R.attr.mediumContrastTextColor);
+
-        reverseTextColor = res.getColor(R.attr.highContrastReverseTextColor);
+        textColors = new int[3];
+        textColors[2] = res.getColor(R.attr.highContrastReverseTextColor);
+        textColors[1] = res.getColor(R.attr.mediumContrastTextColor);
+        textColors[0] = res.getColor(R.attr.lowContrastReverseTextColor);
     }
 
     private void initPaints()
@@ -271,6 +273,12 @@ public class StreakChart extends View
         return colors[0];
     }
 
+    private int percentageToTextColor(float percentage)
+    {
+        if (percentage >= 0.8f) return textColors[2];
+        return textColors[0];
+    }
+
     private void updateMaxMinLengths()
     {
         maxLength = 0;

uhabits-android/src/main/res/layout/about.xml

@@ -132,6 +132,10 @@
                     style="@style/About.Item"
                     android:text="Victor Yu"/>
 
+                <TextView
+                    style="@style/About.Item"
+                    android:text="Christoph Hennemann"/>
+
             </LinearLayout>
 
             <LinearLayout