ui: Read custom recovery UI values via system property.

The matching change to build system now writes these values as build
properties for recovery image. This allows us dropping the dependency on
Android.mk (as well as having more flexibility to do UI customization).

Also rename a few constant names, as the naming doesn't fully follow the
style guide (which reads "whose value is fixed for the duration of the
program").

Bug: 110380063
Test: Build and flash recovery image on taimen, which uses custom margin
      height. Check the UI and choose `Run graphics test`.
Change-Id: I2c50326123639cb36022f51b62cdeed925d77ba7
diff --git a/vr_ui.cpp b/vr_ui.cpp
index b1ef646..a131a27 100644
--- a/vr_ui.cpp
+++ b/vr_ui.cpp
@@ -16,9 +16,15 @@
 
 #include "vr_ui.h"
 
-#include <minui/minui.h>
+#include <android-base/properties.h>
 
-VrRecoveryUI::VrRecoveryUI() : kStereoOffset(RECOVERY_UI_VR_STEREO_OFFSET) {}
+#include "minui/minui.h"
+
+constexpr int kDefaultStereoOffset = 0;
+
+VrRecoveryUI::VrRecoveryUI()
+    : stereo_offset_(
+          android::base::GetIntProperty("ro.recovery.ui.stereo_offset", kDefaultStereoOffset)) {}
 
 int VrRecoveryUI::ScreenWidth() const {
   return gr_fb_width() / 2;
@@ -30,36 +36,37 @@
 
 void VrRecoveryUI::DrawSurface(GRSurface* surface, int sx, int sy, int w, int h, int dx,
                                int dy) const {
-  gr_blit(surface, sx, sy, w, h, dx + kStereoOffset, dy);
-  gr_blit(surface, sx, sy, w, h, dx - kStereoOffset + ScreenWidth(), dy);
+  gr_blit(surface, sx, sy, w, h, dx + stereo_offset_, dy);
+  gr_blit(surface, sx, sy, w, h, dx - stereo_offset_ + ScreenWidth(), dy);
 }
 
 void VrRecoveryUI::DrawTextIcon(int x, int y, GRSurface* surface) const {
-  gr_texticon(x + kStereoOffset, y, surface);
-  gr_texticon(x - kStereoOffset + ScreenWidth(), y, surface);
+  gr_texticon(x + stereo_offset_, y, surface);
+  gr_texticon(x - stereo_offset_ + ScreenWidth(), y, surface);
 }
 
 int VrRecoveryUI::DrawTextLine(int x, int y, const std::string& line, bool bold) const {
-  gr_text(gr_sys_font(), x + kStereoOffset, y, line.c_str(), bold);
-  gr_text(gr_sys_font(), x - kStereoOffset + ScreenWidth(), y, line.c_str(), bold);
+  gr_text(gr_sys_font(), x + stereo_offset_, y, line.c_str(), bold);
+  gr_text(gr_sys_font(), x - stereo_offset_ + ScreenWidth(), y, line.c_str(), bold);
   return char_height_ + 4;
 }
 
 int VrRecoveryUI::DrawHorizontalRule(int y) const {
   y += 4;
-  gr_fill(kMarginWidth + kStereoOffset, y, ScreenWidth() - kMarginWidth + kStereoOffset, y + 2);
-  gr_fill(ScreenWidth() + kMarginWidth - kStereoOffset, y,
-          gr_fb_width() - kMarginWidth - kStereoOffset, y + 2);
+  gr_fill(margin_width_ + stereo_offset_, y, ScreenWidth() - margin_width_ + stereo_offset_, y + 2);
+  gr_fill(ScreenWidth() + margin_width_ - stereo_offset_, y,
+          gr_fb_width() - margin_width_ - stereo_offset_, y + 2);
   return y + 4;
 }
 
 void VrRecoveryUI::DrawHighlightBar(int /* x */, int y, int /* width */, int height) const {
-  gr_fill(kMarginWidth + kStereoOffset, y, ScreenWidth() - kMarginWidth + kStereoOffset, y + height);
-  gr_fill(ScreenWidth() + kMarginWidth - kStereoOffset, y,
-          gr_fb_width() - kMarginWidth - kStereoOffset, y + height);
+  gr_fill(margin_width_ + stereo_offset_, y, ScreenWidth() - margin_width_ + stereo_offset_,
+          y + height);
+  gr_fill(ScreenWidth() + margin_width_ - stereo_offset_, y,
+          gr_fb_width() - margin_width_ - stereo_offset_, y + height);
 }
 
 void VrRecoveryUI::DrawFill(int x, int y, int w, int h) const {
-  gr_fill(x + kStereoOffset, y, w, h);
-  gr_fill(x - kStereoOffset + ScreenWidth(), y, w, h);
+  gr_fill(x + stereo_offset_, y, w, h);
+  gr_fill(x - stereo_offset_ + ScreenWidth(), y, w, h);
 }