Generic display: add period to the end of the line in case of truncate

doc/documentation.md

@@ -526,6 +526,20 @@ Here the ```dot_position``` option is an index starting at the most right positi
 | ------| -------------- | -------------- | -------------- |
 | 12345 | 12345.         | 1234.5         | 123.45         |
 
+### Display Value Truncation
+#### Overview
+When displaying values on hardware panels with limited character capacity, XPanel automatically handles cases where the data exceeds the available display space.
+
+#### Truncation Behavior
+If a display value is wider than the available characters on the hardware display, XPanel will truncate the value and append a period (`.`) character at the end to indicate that the value has been shortened.
+
+**Example:**
+- **Full value**: `120.375` (8.33kHz radio frequency)
+- **Saitek Radio Panel display** (5 characters): `12037.`
+- The period at the end indicates that the complete value cannot be displayed
+
+#### Configuration
+The truncation behavior is automatically applied and does not require any configuration. The feature ensures that users are always aware when displayed values are incomplete due to hardware limitations.
 
 ### Multipurpose displays
 The display value can be a conditional display which means the value to display depends on the position of a switch. A display that contains conditions called multi-purpose display (multi_display).

src/core/GenericDisplay.cpp

@@ -161,17 +161,29 @@ bool GenericDisplay::get_decimal_components(int number, unsigned char* buffer, i
 		negative = true;
 	}
 
-	if (number > pow(10, nr_of_bytes))
-		return false;
+	for (int i = 0; i < nr_of_bytes; i++)
+		buffer[i] = ZERO_CHAR;
 
-	int remain = number;
-	for (int dec_pos = nr_of_bytes - 1; dec_pos >= 0; dec_pos--)
+	if (number != 0)
 	{
-		buffer[nr_of_bytes - 1 - dec_pos] = remain / (int)pow(10, dec_pos);
-		if (dec_pos == _dot_position)
-			buffer[nr_of_bytes - 1 - dec_pos] += PERIOD_CHAR; // turn on period dot
+		// how many decimal positions do we need?
+		const int base_10_of_number = (int)log10(number);
+
+		int remain = number;
+		int buffer_index = nr_of_bytes > (base_10_of_number + 1) ? nr_of_bytes - (base_10_of_number+1) : 0;
+
+		for (int dec_pos = base_10_of_number; dec_pos >= 0 && buffer_index < nr_of_bytes; dec_pos--)
+		{
+			buffer[buffer_index] = remain / (int)pow(10, dec_pos);
+			if (dec_pos == _dot_position)
+				buffer[buffer_index] += PERIOD_CHAR; // turn on period dot
+
+			remain = remain % (int)pow(10, dec_pos);
+			buffer_index++;
+		}
 
-		remain = remain % (int)pow(10, dec_pos);
+		if (remain != 0)
+			buffer[nr_of_bytes - 1] += PERIOD_CHAR; // a dot at the end of display indicates the truncated line
 	}
 
 	if (blank_leading_zeros)

test/test-radio-panel-config.ini

@@ -10,11 +10,12 @@ pid="d05"
 
 [multi_display:id="RADIO_DISPLAY_ACTIVE_UP"]
 line="on_select:SW_UP_COM1,dataref:sim/cockpit2/radios/actuators/com1_frequency_hz"
-line="on_select:SW_UP_COM2,dataref:sim/cockpit/radios/com1_stdby_freq_hz"
+line="on_select:SW_UP_COM2,dataref:sim/cockpit2/radios/actuators/com1_frequency_hz_833"
 line="on_select:SW_UP_NAV1,dataref:sim/cockpit2/radios/actuators/nav1_frequency_hz"
 line="on_select:SW_UP_NAV2,dataref:sim/cockpit2/radios/actuators/nav2_frequency_hz"
 line="on_select:SW_UP_ADF,const:12345"
 line="on_select:SW_UP_DME,lua:get_display_value()"
+line="on_select:SW_UP_IDT,dataref:sim/cockpit2/radios/actuators/transponder_code"
 
 [button:id="KNOB_UP_BIG_PLUS"]
 on_push="on_select:SW_UP_COM1,dataref:sim/cockpit2/radios/actuators/com1_frequency_hz:100:0:99999"

test/test_radio_panel.cpp

@@ -39,11 +39,15 @@ namespace test
 		std::string nav2_freq_dataref_str = "sim/cockpit2/radios/actuators/nav2_frequency_hz";
 		std::string com1_freq_dataref_str = "sim/cockpit2/radios/actuators/com1_frequency_hz";
 		std::string com2_freq_dataref_str = "sim/cockpit/radios/com1_stdby_freq_hz";
+		std::string com1_freq_833khz_dataref_str = "sim/cockpit2/radios/actuators/com1_frequency_hz_833";
+		std::string transponder_code_str = "sim/cockpit2/radios/actuators/transponder_code";
 
 		XPLMDataRef nav1_freq_dataref;
 		XPLMDataRef nav2_freq_dataref;
 		XPLMDataRef com1_freq_dataref;
 		XPLMDataRef com2_freq_dataref;
+		XPLMDataRef com1_freq_833khz_dataref;
+		XPLMDataRef transponder_code_dataref;
 
 	public:
 		TEST_METHOD_INITIALIZE(TestMultiPanelInit)
@@ -66,11 +70,15 @@ namespace test
 			nav2_freq_dataref = XPLMFindDataRef(nav2_freq_dataref_str.c_str());
 			com1_freq_dataref = XPLMFindDataRef(com1_freq_dataref_str.c_str());
 			com2_freq_dataref = XPLMFindDataRef(com2_freq_dataref_str.c_str());
+			com1_freq_833khz_dataref = XPLMFindDataRef(com1_freq_833khz_dataref_str.c_str());
+			transponder_code_dataref = XPLMFindDataRef(transponder_code_str.c_str());
 
 			XPLMSetDatai(nav1_freq_dataref, 11111);
 			XPLMSetDatai(nav2_freq_dataref, 22222);
 			XPLMSetDatai(com1_freq_dataref, 33333);
 			XPLMSetDatai(com2_freq_dataref, 44444);
+			XPLMSetDatai(com1_freq_833khz_dataref, 120375); // 120.375 Mhz is a 8.33kHz channel
+			XPLMSetDatai(transponder_code_dataref, 7001);
 		}
 
 		TEST_METHOD(Test_VID_PID)
@@ -98,6 +106,45 @@ namespace test
 			Assert::AreEqual(1, (int)write_buffer[5]);
 		}
 
+		TEST_METHOD(Test_Display_833kHz)
+		{
+			// set rotation switch to SW_COM_2 position
+			unsigned char buffer[4] = { 0x02,0,0,0 };
+			test_hid_set_read_data(buffer, sizeof(buffer));
+			std::this_thread::sleep_for(150ms);
+
+			test_flight_loop(device);
+			std::this_thread::sleep_for(150ms);
+
+			unsigned char write_buffer[23];
+			test_hid_get_write_data(write_buffer, sizeof(write_buffer));
+			Assert::AreEqual(1, (int)write_buffer[1]);
+			Assert::AreEqual(2, (int)write_buffer[2]);
+			Assert::AreEqual(0, (int)write_buffer[3]);
+			Assert::AreEqual(3, (int)write_buffer[4]);
+			Assert::AreEqual(7, (int)write_buffer[5] & 0x0F); // the digit at last position
+			Assert::AreEqual(0xD0, (int)write_buffer[5] & 0xF0); // the period after the last digit
+		}
+
+		TEST_METHOD(Test_4_digit_display)
+		{
+			// set rotation switch to XPDR position
+			unsigned char buffer[4] = { 0x40,0,0,0 };
+			test_hid_set_read_data(buffer, sizeof(buffer));
+			std::this_thread::sleep_for(150ms);
+
+			test_flight_loop(device);
+			std::this_thread::sleep_for(150ms);
+
+			unsigned char write_buffer[23];
+			test_hid_get_write_data(write_buffer, sizeof(write_buffer));
+			Assert::AreEqual(255, (int)write_buffer[1]);
+			Assert::AreEqual(7, (int)write_buffer[2]);
+			Assert::AreEqual(0, (int)write_buffer[3]);
+			Assert::AreEqual(0, (int)write_buffer[4]);
+			Assert::AreEqual(1, (int)write_buffer[5]);
+		}
+
 		TEST_METHOD(Test_Const_Value)
 		{
 			// set rotation switch to SW_UP_ADF position